Rename validation source files to comply with Google style guide.
diff --git a/source/CMakeLists.txt b/source/CMakeLists.txt
index 5439ecf..0c6ff93 100644
--- a/source/CMakeLists.txt
+++ b/source/CMakeLists.txt
@@ -160,11 +160,11 @@
   ${CMAKE_CURRENT_SOURCE_DIR}/validate_instruction.cpp
   ${CMAKE_CURRENT_SOURCE_DIR}/validate_datarules.cpp
   ${CMAKE_CURRENT_SOURCE_DIR}/validate_layout.cpp
-  ${CMAKE_CURRENT_SOURCE_DIR}/val/BasicBlock.cpp
-  ${CMAKE_CURRENT_SOURCE_DIR}/val/Construct.cpp
-  ${CMAKE_CURRENT_SOURCE_DIR}/val/Function.cpp
-  ${CMAKE_CURRENT_SOURCE_DIR}/val/Instruction.cpp
-  ${CMAKE_CURRENT_SOURCE_DIR}/val/ValidationState.cpp)
+  ${CMAKE_CURRENT_SOURCE_DIR}/val/basic_block.cpp
+  ${CMAKE_CURRENT_SOURCE_DIR}/val/construct.cpp
+  ${CMAKE_CURRENT_SOURCE_DIR}/val/function.cpp
+  ${CMAKE_CURRENT_SOURCE_DIR}/val/instruction.cpp
+  ${CMAKE_CURRENT_SOURCE_DIR}/val/validation_state.cpp)
 
 # The software_version.cpp file includes build-version.inc.
 # Rebuild the software_version.cpp object file if it is older than
diff --git a/source/val/BasicBlock.cpp b/source/val/basic_block.cpp
similarity index 99%
rename from source/val/BasicBlock.cpp
rename to source/val/basic_block.cpp
index 55483b9..0bfc4f1 100644
--- a/source/val/BasicBlock.cpp
+++ b/source/val/basic_block.cpp
@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#include "BasicBlock.h"
+#include "val/basic_block.h"
 
 #include <algorithm>
 #include <utility>
diff --git a/source/val/BasicBlock.h b/source/val/basic_block.h
similarity index 100%
rename from source/val/BasicBlock.h
rename to source/val/basic_block.h
diff --git a/source/val/Construct.cpp b/source/val/construct.cpp
similarity index 98%
rename from source/val/Construct.cpp
rename to source/val/construct.cpp
index da87b4d..4270063 100644
--- a/source/val/Construct.cpp
+++ b/source/val/construct.cpp
@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#include "val/Construct.h"
+#include "val/construct.h"
 
 #include <cassert>
 #include <cstddef>
diff --git a/source/val/Construct.h b/source/val/construct.h
similarity index 100%
rename from source/val/Construct.h
rename to source/val/construct.h
diff --git a/source/val/Function.cpp b/source/val/function.cpp
similarity index 99%
rename from source/val/Function.cpp
rename to source/val/function.cpp
index 223fcb1..e033bfe 100644
--- a/source/val/Function.cpp
+++ b/source/val/function.cpp
@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#include "val/Function.h"
+#include "val/function.h"
 
 #include <cassert>
 
@@ -21,8 +21,8 @@
 #include <unordered_map>
 #include <utility>
 
-#include "val/BasicBlock.h"
-#include "val/Construct.h"
+#include "val/basic_block.h"
+#include "val/construct.h"
 #include "validate.h"
 
 using std::ignore;
diff --git a/source/val/Function.h b/source/val/function.h
similarity index 99%
rename from source/val/Function.h
rename to source/val/function.h
index dc5c324..bd993c7 100644
--- a/source/val/Function.h
+++ b/source/val/function.h
@@ -15,16 +15,16 @@
 #ifndef LIBSPIRV_VAL_FUNCTION_H_
 #define LIBSPIRV_VAL_FUNCTION_H_
 
-#include <list>
 #include <functional>
+#include <list>
 #include <unordered_map>
 #include <unordered_set>
 #include <vector>
 
 #include "spirv-tools/libspirv.h"
 #include "spirv/1.1/spirv.h"
-#include "val/BasicBlock.h"
-#include "val/Construct.h"
+#include "val/basic_block.h"
+#include "val/construct.h"
 
 namespace libspirv {
 
diff --git a/source/val/Instruction.cpp b/source/val/instruction.cpp
similarity index 98%
rename from source/val/Instruction.cpp
rename to source/val/instruction.cpp
index 02be245..56bd37f 100644
--- a/source/val/Instruction.cpp
+++ b/source/val/instruction.cpp
@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#include "val/Instruction.h"
+#include "val/instruction.h"
 
 #include <utility>
 
diff --git a/source/val/Instruction.h b/source/val/instruction.h
similarity index 100%
rename from source/val/Instruction.h
rename to source/val/instruction.h
diff --git a/source/val/ValidationState.cpp b/source/val/validation_state.cpp
similarity index 98%
rename from source/val/ValidationState.cpp
rename to source/val/validation_state.cpp
index 1368416..11096bc 100644
--- a/source/val/ValidationState.cpp
+++ b/source/val/validation_state.cpp
@@ -12,13 +12,13 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#include "val/ValidationState.h"
+#include "val/validation_state.h"
 
 #include <cassert>
 
-#include "val/BasicBlock.h"
-#include "val/Construct.h"
-#include "val/Function.h"
+#include "val/basic_block.h"
+#include "val/construct.h"
+#include "val/function.h"
 
 using std::deque;
 using std::make_pair;
diff --git a/source/val/ValidationState.h b/source/val/validation_state.h
similarity index 98%
rename from source/val/ValidationState.h
rename to source/val/validation_state.h
index ff23d05..006f055 100644
--- a/source/val/ValidationState.h
+++ b/source/val/validation_state.h
@@ -27,8 +27,8 @@
 #include "spirv-tools/libspirv.h"
 #include "spirv/1.1/spirv.h"
 #include "spirv_definition.h"
-#include "val/Function.h"
-#include "val/Instruction.h"
+#include "val/function.h"
+#include "val/instruction.h"
 
 namespace libspirv {
 
diff --git a/source/validate.cpp b/source/validate.cpp
index d253d17..2898497 100644
--- a/source/validate.cpp
+++ b/source/validate.cpp
@@ -32,9 +32,9 @@
 #include "spirv-tools/libspirv.h"
 #include "spirv_constant.h"
 #include "spirv_endian.h"
-#include "val/Construct.h"
-#include "val/Function.h"
-#include "val/ValidationState.h"
+#include "val/construct.h"
+#include "val/function.h"
+#include "val/validation_state.h"
 
 using std::function;
 using std::ostream_iterator;
diff --git a/source/validate_cfg.cpp b/source/validate_cfg.cpp
index 7843697..b01b88d 100644
--- a/source/validate_cfg.cpp
+++ b/source/validate_cfg.cpp
@@ -26,10 +26,10 @@
 #include <utility>
 #include <vector>
 
-#include "val/BasicBlock.h"
-#include "val/Construct.h"
-#include "val/Function.h"
-#include "val/ValidationState.h"
+#include "val/basic_block.h"
+#include "val/construct.h"
+#include "val/function.h"
+#include "val/validation_state.h"
 
 using std::find;
 using std::function;
diff --git a/source/validate_datarules.cpp b/source/validate_datarules.cpp
index d21c33b..c6626b8 100644
--- a/source/validate_datarules.cpp
+++ b/source/validate_datarules.cpp
@@ -23,7 +23,7 @@
 #include "diagnostic.h"
 #include "opcode.h"
 #include "operand.h"
-#include "val/ValidationState.h"
+#include "val/validation_state.h"
 
 using libspirv::CapabilitySet;
 using libspirv::DiagnosticStream;
diff --git a/source/validate_id.cpp b/source/validate_id.cpp
index bd7f206..f603a06 100644
--- a/source/validate_id.cpp
+++ b/source/validate_id.cpp
@@ -27,8 +27,8 @@
 #include "message.h"
 #include "opcode.h"
 #include "spirv-tools/libspirv.h"
-#include "val/Function.h"
-#include "val/ValidationState.h"
+#include "val/function.h"
+#include "val/validation_state.h"
 
 using libspirv::ValidationState_t;
 using std::function;
diff --git a/source/validate_instruction.cpp b/source/validate_instruction.cpp
index 8160b10..bcab49a 100644
--- a/source/validate_instruction.cpp
+++ b/source/validate_instruction.cpp
@@ -26,8 +26,8 @@
 #include "opcode.h"
 #include "operand.h"
 #include "spirv_definition.h"
-#include "val/Function.h"
-#include "val/ValidationState.h"
+#include "val/function.h"
+#include "val/validation_state.h"
 
 using libspirv::AssemblyGrammar;
 using libspirv::CapabilitySet;
diff --git a/source/validate_layout.cpp b/source/validate_layout.cpp
index de650b4..b8b5518 100644
--- a/source/validate_layout.cpp
+++ b/source/validate_layout.cpp
@@ -22,8 +22,8 @@
 #include "opcode.h"
 #include "operand.h"
 #include "spirv-tools/libspirv.h"
-#include "val/Function.h"
-#include "val/ValidationState.h"
+#include "val/function.h"
+#include "val/validation_state.h"
 
 using libspirv::ValidationState_t;
 using libspirv::kLayoutMemoryModel;
diff --git a/test/val/val_state_test.cpp b/test/val/val_state_test.cpp
index d6635e0..2e6dafb 100644
--- a/test/val/val_state_test.cpp
+++ b/test/val/val_state_test.cpp
@@ -21,9 +21,9 @@
 #include "spirv/1.1/spirv.h"
 
 #include "enum_set.h"
-#include "val/Construct.h"
-#include "val/Function.h"
-#include "val/ValidationState.h"
+#include "val/construct.h"
+#include "val/function.h"
+#include "val/validation_state.h"
 #include "validate.h"
 
 namespace {