Fix double-accounting of SkPictureShader bitmap memory

The pixels RAM is accounted via SkImageGenerator/SkImageCacherator, we
don't need to report it as part of SkPictureShader's BitmapShaderRec.

R=reed@google.com
BUG=chromium:619929
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2415673002

Review-Url: https://codereview.chromium.org/2415673002
diff --git a/src/core/SkPictureShader.cpp b/src/core/SkPictureShader.cpp
index 3349558..c7ceb76 100644
--- a/src/core/SkPictureShader.cpp
+++ b/src/core/SkPictureShader.cpp
@@ -11,6 +11,7 @@
 #include "SkBitmapProcShader.h"
 #include "SkCanvas.h"
 #include "SkImage.h"
+#include "SkImageShader.h"
 #include "SkMatrixUtils.h"
 #include "SkPicture.h"
 #include "SkReadBuffer.h"
@@ -63,10 +64,9 @@
 };
 
 struct BitmapShaderRec : public SkResourceCache::Rec {
-    BitmapShaderRec(const BitmapShaderKey& key, SkShader* tileShader, size_t bitmapBytes)
+    BitmapShaderRec(const BitmapShaderKey& key, SkShader* tileShader)
         : fKey(key)
-        , fShader(SkRef(tileShader))
-        , fBitmapBytes(bitmapBytes) {}
+        , fShader(SkRef(tileShader)) {}
 
     BitmapShaderKey        fKey;
     SkAutoTUnref<SkShader> fShader;
@@ -74,7 +74,8 @@
 
     const Key& getKey() const override { return fKey; }
     size_t bytesUsed() const override {
-        return sizeof(fKey) + sizeof(SkShader) + fBitmapBytes;
+        // Just the record overhead -- the actual pixels are accounted by SkImageCacherator.
+        return sizeof(fKey) + sizeof(SkImageShader);
     }
     const char* getCategory() const override { return "bitmap-shader"; }
     SkDiscardableMemory* diagnostic_only_getDiscardable() const override { return nullptr; }
@@ -233,9 +234,7 @@
         shaderMatrix.preScale(1 / tileScale.width(), 1 / tileScale.height());
         tileShader = tileImage->makeShader(fTmx, fTmy, &shaderMatrix);
 
-        const SkImageInfo tileInfo = SkImageInfo::MakeN32Premul(tileSize);
-        SkResourceCache::Add(new BitmapShaderRec(key, tileShader.get(),
-                                                 tileInfo.getSafeSize(tileInfo.minRowBytes())));
+        SkResourceCache::Add(new BitmapShaderRec(key, tileShader.get()));
     }
 
     return tileShader;