Move ICCTag struct and GetTag functions to skcms_internal.h

Clients can't do anything with this API, so let's avoid tempting them.

Change-Id: I647f40bd31be665648ffcdea1a89e6381721431f
Reviewed-on: https://skia-review.googlesource.com/c/skcms/+/253936
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
diff --git a/fuzz/fuzz_iccprofile_info.c b/fuzz/fuzz_iccprofile_info.c
index 48da5db..a9f5b4f 100644
--- a/fuzz/fuzz_iccprofile_info.c
+++ b/fuzz/fuzz_iccprofile_info.c
@@ -9,6 +9,7 @@
 // of info from it.
 
 #include "../skcms.h"
+#include "../skcms_internal.h"
 
 static volatile uint32_t g_FoolTheOptimizer = 0;
 
diff --git a/skcms.h b/skcms.h
index 789f975..3df6b44 100644
--- a/skcms.h
+++ b/skcms.h
@@ -176,16 +176,6 @@
                                       skcms_TransferFunction* approx,
                                       float* max_error);
 
-typedef struct skcms_ICCTag {
-    uint32_t       signature;
-    uint32_t       type;
-    uint32_t       size;
-    const uint8_t* buf;
-} skcms_ICCTag;
-
-SKCMS_API void skcms_GetTagByIndex    (const skcms_ICCProfile*, uint32_t idx, skcms_ICCTag*);
-SKCMS_API bool skcms_GetTagBySignature(const skcms_ICCProfile*, uint32_t sig, skcms_ICCTag*);
-
 SKCMS_API bool skcms_GetCHAD(const skcms_ICCProfile*, skcms_Matrix3x3*);
 SKCMS_API bool skcms_GetWTPT(const skcms_ICCProfile*, float xyz[3]);
 
diff --git a/skcms_internal.h b/skcms_internal.h
index 3a82ec7..0eaa9dd 100644
--- a/skcms_internal.h
+++ b/skcms_internal.h
@@ -21,6 +21,16 @@
 // ~~~~ General Helper Macros ~~~~
     #define ARRAY_COUNT(arr) (int)(sizeof((arr)) / sizeof(*(arr)))
 
+    typedef struct skcms_ICCTag {
+        uint32_t       signature;
+        uint32_t       type;
+        uint32_t       size;
+        const uint8_t* buf;
+    } skcms_ICCTag;
+
+    void skcms_GetTagByIndex    (const skcms_ICCProfile*, uint32_t idx, skcms_ICCTag*);
+    bool skcms_GetTagBySignature(const skcms_ICCProfile*, uint32_t sig, skcms_ICCTag*);
+
     // 252 of a random shuffle of all possible bytes.
     // 252 is evenly divisible by 3 and 4.  Only 192, 10, 241, and 43 are missing.
     // Used for ICC profile equivalence testing.