Teach Skia to use discardable memory

Source/web/tests/DeferredImageDecoderTest.cpp

Index: Source/web/tests/DeferredImageDecoderTest.cpp
diff --git a/Source/web/tests/DeferredImageDecoderTest.cpp b/Source/web/tests/DeferredImageDecoderTest.cpp
index 29c0e3ec732f1cbef384338365d8d84807cd5eb0..fc35db28192c3e19a0895be036214e2def36f04d 100644
--- a/Source/web/tests/DeferredImageDecoderTest.cpp
+++ b/Source/web/tests/DeferredImageDecoderTest.cpp
@@ -176,6 +176,34 @@ TEST_F(DeferredImageDecoderTest, drawIntoSkPicture)
     EXPECT_EQ(SkColorSetARGB(255, 255, 255, 255), canvasBitmap.getColor(0, 0));
 }
 
+TEST_F(DeferredImageDecoderTest, drawDiscardableIntoSkPicture)
+{
+    DeferredImageDecoder::setSkiaDiscardableMemoryEnabled(true);
+
+    m_lazyDecoder->setData(m_data.get(), true);
+    RefPtr<NativeImageSkia> image = m_lazyDecoder->frameBufferAtIndex(0)->asNewNativeImage();
+    EXPECT_EQ(1, image->bitmap().width());
+    EXPECT_EQ(1, image->bitmap().height());
+    EXPECT_FALSE(image->bitmap().isNull());
+    EXPECT_TRUE(image->bitmap().isImmutable());
+
+    SkCanvas* tempCanvas = m_picture.beginRecording(100, 100);
+    tempCanvas->drawBitmap(image->bitmap(), 0, 0);
+    m_picture.endRecording();
+    EXPECT_EQ(0, m_frameBufferRequestCount);
+
+    m_canvas->drawPicture(m_picture);
+    EXPECT_EQ(0, m_frameBufferRequestCount);
+
+    SkBitmap canvasBitmap;
+    canvasBitmap.setConfig(SkBitmap::kARGB_8888_Config, 100, 100);
+    ASSERT_TRUE(m_canvas->readPixels(&canvasBitmap, 0, 0));
+    SkAutoLockPixels autoLock(canvasBitmap);
+    EXPECT_EQ(SkColorSetARGB(255, 255, 255, 255), canvasBitmap.getColor(0, 0));
+
+    DeferredImageDecoder::setSkiaDiscardableMemoryEnabled(false);
+}
+
 TEST_F(DeferredImageDecoderTest, DISABLED_drawScaledIntoSkPicture)
 {
     m_lazyDecoder->setData(m_data.get(), true);