Add SkPaint::getHash().

src/core/SkPaint.cpp

Index: src/core/SkPaint.cpp
diff --git a/src/core/SkPaint.cpp b/src/core/SkPaint.cpp
index 7ce7fc9ccd19df02b740bb96c38e934d63c7974d..a25ec1d333902ad6b194339c8f6cdfca4c10a0a0 100644
--- a/src/core/SkPaint.cpp
+++ b/src/core/SkPaint.cpp
@@ -8,6 +8,7 @@
 #include "SkPaint.h"
 #include "SkAnnotation.h"
 #include "SkAutoKern.h"
+#include "SkChecksum.h"
 #include "SkColorFilter.h"
 #include "SkData.h"
 #include "SkDeviceProperties.h"
@@ -2460,3 +2461,11 @@ bool SkPaint::nothingToDraw() const {
     return false;
 }
 
+uint32_t SkPaint::getHash() const {
+    // We're going to hash 10 pointers and 7 32-bit values, finishing up with fBitfields,
+    // so fBitfields should be 10 pointers and 6 32-bit values from the start.
+    SK_COMPILE_ASSERT(offsetof(SkPaint, fBitfields) == 10 * sizeof(void*) + 6 * sizeof(uint32_t),
+                      SkPaint_notPackedTightly);
+    return SkChecksum::Murmur3(reinterpret_cast<const uint32_t*>(this),
+                               offsetof(SkPaint, fBitfields) + sizeof(fBitfields));
+}