Clean up Skia for Clang's -Wtautological-undefined-compare

This is blocking Chrome from rolling a new Clang, and me too for our TSAN bots.

BUG=chromium:381910

Review URL: https://codereview.chromium.org/325603002

include/core/SkTLazy.h

diff --git a/include/core/SkTLazy.h b/include/core/SkTLazy.h
index 518beec..a291e22 100644
--- a/include/core/SkTLazy.h
+++ b/include/core/SkTLazy.h
@@ -66,11 +66,6 @@
      *  contents.
      */
     T* set(const T& src) {
-        // Diagnoistic. May remove later. See crbug.com/364224
-        if (NULL == &src) {
-            sk_throw();
-        }
-
         if (this->isValid()) {
             *fPtr = src;
         } else {

src/core/SkPaint.cpp

diff --git a/src/core/SkPaint.cpp b/src/core/SkPaint.cpp
index f3bf01b..78d9470 100644
--- a/src/core/SkPaint.cpp
+++ b/src/core/SkPaint.cpp
@@ -106,11 +106,6 @@
 }
 
 SkPaint::SkPaint(const SkPaint& src) {
-    // Diagnoistic. May remove later. See crbug.com/364224
-    if (NULL == &src) {
-        sk_throw();
-    }
-
 #define COPY(field) field = src.field
 #define REF_COPY(field) field = SkSafeRef(src.field)
 

src/core/SkRegion.cpp

diff --git a/src/core/SkRegion.cpp b/src/core/SkRegion.cpp
index 98670b6..24d7248 100644
--- a/src/core/SkRegion.cpp
+++ b/src/core/SkRegion.cpp
@@ -212,12 +212,6 @@
 ///////////////////////////////////////////////////////////////////////////////
 
 int SkRegion::count_runtype_values(int* itop, int* ibot) const {
-    if (this == NULL) {
-        *itop = SK_MinS32;
-        *ibot = SK_MaxS32;
-        return 0;
-    }
-
     int maxT;
 
     if (this->isRect()) {