blimp: Reduce WebP encoding time on the engine.

blimp/engine/renderer/engine_image_serialization_processor.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "blimp/engine/renderer/engine_image_serialization_processor.h"
 
 #include <stddef.h>
 #include <vector>
 
 #include "base/logging.h"
@@ skipping 49 matching lines @@
     std::vector<unsigned char> data;
     picture.custom_ptr = &data;
 
     // Use our own WebPWriterFunction implementation.
     picture.writer = &WebPImageEncoder::WriteOutput;
 
     // Setup the configuration for the output WebP picture. This is currently
     // the same as the default configuration for WebP, but since any change in
     // the WebP defaults would invalidate all caches they are hard coded.
     config.quality = 75.0;  // between 0 (smallest file) and 100 (biggest).
-    config.method = 4;  // quality/speed trade-off (0=fast, 6=slower-better).
+
+    // TODO(nyquist): Move image encoding to a different thread when
+    // asynchronous loading of images is possible. The encode work currently
+    // blocks the render thread so we are dropping the method down to 0.
+    // crbug.com/603643.
+    config.method = 0;  // quality/speed trade-off (0=fast, 6=slower-better).
 
     // Encode the picture using the given configuration.
     bool success = WebPEncode(&config, &picture);
 
     // Release the memory allocated by WebPPictureImport*(). This does not free
     // the memory used by the picture object itself.
     WebPPictureFree(&picture);
 
     if (!success)
       return nullptr;
@@ skipping 79 matching lines @@
   return pixel_serializer_.get();
 }
 
 SkPicture::InstallPixelRefProc
 EngineImageSerializationProcessor::GetPixelDeserializer() {
   return nullptr;
 }
 
 }  // namespace engine
 }  // namespace blimp