Cheaper thread-safe atomic initialization of static references.

Source/platform/graphics/ImageFrameGeneratorTest.cpp

Index: Source/platform/graphics/ImageFrameGeneratorTest.cpp
diff --git a/Source/platform/graphics/ImageFrameGeneratorTest.cpp b/Source/platform/graphics/ImageFrameGeneratorTest.cpp
index 129dfd67b79fe0b3fc7545cf0abe28600a5a1a41..12072e8e881196238264ee276c976babff3607c6 100644
--- a/Source/platform/graphics/ImageFrameGeneratorTest.cpp
+++ b/Source/platform/graphics/ImageFrameGeneratorTest.cpp
@@ -52,7 +52,7 @@ class ImageFrameGeneratorTest : public ::testing::Test, public MockImageDecoderC
 public:
     virtual void SetUp() override
     {
-        ImageDecodingStore::instance()->setCacheLimitInBytes(1024 * 1024);
+        ImageDecodingStore::instance().setCacheLimitInBytes(1024 * 1024);
         m_data = SharedBuffer::create();
         m_generator = ImageFrameGenerator::create(fullSize(), m_data, false);
         useMockImageDecoderFactory();
@@ -64,7 +64,7 @@ public:
 
     virtual void TearDown() override
     {
-        ImageDecodingStore::instance()->clear();
+        ImageDecodingStore::instance().clear();
     }
 
     virtual void decoderBeingDestroyed() override
@@ -195,10 +195,10 @@ TEST_F(ImageFrameGeneratorTest, frameHasAlpha)
     EXPECT_EQ(1, m_frameBufferRequestCount);
 
     ImageDecoder* tempDecoder = 0;
-    EXPECT_TRUE(ImageDecodingStore::instance()->lockDecoder(m_generator.get(), fullSize(), &tempDecoder));
+    EXPECT_TRUE(ImageDecodingStore::instance().lockDecoder(m_generator.get(), fullSize(), &tempDecoder));
     ASSERT_TRUE(tempDecoder);
     static_cast<MockImageDecoder*>(tempDecoder)->setFrameHasAlpha(false);
-    ImageDecodingStore::instance()->unlockDecoder(m_generator.get(), tempDecoder);
+    ImageDecodingStore::instance().unlockDecoder(m_generator.get(), tempDecoder);
 
     setFrameStatus(ImageFrame::FrameComplete);
     m_generator->decodeAndScale(imageInfo(), 0, buffer, 100 * 4);