Refactoring of GPU NormalMap handling out into its own class

src/core/SkBitmapProcShader.h

Index: src/core/SkBitmapProcShader.h
diff --git a/src/core/SkBitmapProcShader.h b/src/core/SkBitmapProcShader.h
index 1d374335c2a46b0a2ac3bc66924a891ffe1b069f..5f0b5eeffe526345de475c43fb3fca734871c059 100644
--- a/src/core/SkBitmapProcShader.h
+++ b/src/core/SkBitmapProcShader.h
@@ -21,6 +21,11 @@ public:
 
     bool isOpaque() const override;
 
+    // SkBitmapProcShader stores bitmap coordinates in a 16bit buffer, as it
+    // communicates between its matrix-proc and its sampler-proc. Until we can
+    // widen that, we have to reject bitmaps that are larger.
+    static bool BitmapIsTooBig(const SkBitmap&);
+
     SK_TO_STRING_OVERRIDE()
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkBitmapProcShader)