remove unused cachedBitmap from ImageBufferSurface

Source/platform/graphics/ImageBuffer.cpp

 /*
  * Copyright (c) 2008, Google Inc. All rights reserved.
  * Copyright (C) 2009 Dirk Schulze <krit@webkit.org>
  * Copyright (C) 2010 Torch Mobile (Beijing) Co. Ltd. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
@@ skipping 223 matching lines @@
     if (!context3D || !textureImage)
         return false;
     ASSERT(textureImage->isTextureBacked());
     // Get the texture ID, flushing pending operations if needed.
     Platform3DObject textureId = textureImage->getTextureHandle(true);
     if (!textureId)
         return false;
 
     context3D->flush();
 
-    m_surface->invalidateCachedBitmap();
     bool result = drawingBuffer->copyToPlatformTexture(context3D, textureId, GL_RGBA,
         GL_UNSIGNED_BYTE, 0, true, false, sourceBuffer);
 
     if (result) {
         m_surface->didModifyBackingTexture();
     }
 
     return result;
 }
 
@@ skipping 122 matching lines @@
     ASSERT(MIMETypeRegistry::isSupportedImageMIMETypeForEncoding(mimeType));
 
     Vector<char> encodedImage;
     if (!encodeImage(*this, mimeType, quality, &encodedImage))
         return "data:,";
 
     return "data:" + mimeType + ";base64," + base64Encode(encodedImage);
 }
 
 } // namespace blink