Add WebKitUnitTestSupport::readFromFile and deprecate all PlatformFileHandle related methods

Source/core/platform/image-decoders/webp/WEBPImageDecoderTest.cpp

Index: Source/core/platform/image-decoders/webp/WEBPImageDecoderTest.cpp
diff --git a/Source/core/platform/image-decoders/webp/WEBPImageDecoderTest.cpp b/Source/core/platform/image-decoders/webp/WEBPImageDecoderTest.cpp
index da9ee8e8e3f372feda912ee8d6ce3cb9a2538791..002ae08d4c9e26aec93d419078993eda362bb1ff 100644
--- a/Source/core/platform/image-decoders/webp/WEBPImageDecoderTest.cpp
+++ b/Source/core/platform/image-decoders/webp/WEBPImageDecoderTest.cpp
@@ -33,7 +33,6 @@
 #include "core/platform/image-decoders/webp/WEBPImageDecoder.h"
 
 #include "RuntimeEnabledFeatures.h"
-#include "core/platform/FileSystem.h"
 #include "core/platform/SharedBuffer.h"
 #include "public/platform/Platform.h"
 #include "public/platform/WebData.h"
@@ -58,16 +57,7 @@ PassRefPtr<SharedBuffer> readFile(const char* fileName)
     String filePath = Platform::current()->unitTestSupport()->webKitRootDir();
     filePath.append(fileName);
 
-    long long fileSize;
-    if (!getFileSize(filePath, fileSize))
-        return 0;
-
-    PlatformFileHandle handle = openFile(filePath, OpenForRead);
-    int fileLength = static_cast<int>(fileSize);
-    Vector<char> buffer(fileLength);
-    readFromFile(handle, buffer.data(), fileLength);
-    closeFile(handle);
-    return SharedBuffer::adoptVector(buffer);
+    return Platform::current()->unitTestSupport()->readFromFile(filePath);
 }
 
 PassOwnPtr<WEBPImageDecoder> createDecoder()
@@ -443,4 +433,3 @@ TEST_F(AnimatedWebPTests, resumePartialDecodeAfterClearFrameBufferCache)
 }
 
 #endif
-