Improving GestureNav screenshotting performance - part 2 - GestureNav

content/browser/frame_host/navigation_entry_screenshot_manager.cc

 // Copyright 2013 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 "content/browser/frame_host/navigation_entry_screenshot_manager.h"
 
 #include "base/command_line.h"
 #include "base/threading/worker_pool.h"
 #include "content/browser/frame_host/navigation_controller_impl.h"
 #include "content/browser/frame_host/navigation_entry_impl.h"
 #include "content/browser/renderer_host/render_view_host_impl.h"
 #include "content/public/browser/overscroll_configuration.h"
 #include "content/public/browser/render_widget_host.h"
 #include "content/public/browser/render_widget_host_view.h"
 #include "content/public/common/content_switches.h"
-#include "third_party/skia/include/core/SkCanvas.h"
-#include "third_party/skia/include/core/SkPaint.h"
-#include "third_party/skia/include/effects/SkLumaColorFilter.h"
 #include "ui/gfx/codec/png_codec.h"
 
 namespace {
 
 // Minimum delay between taking screenshots.
 const int kMinScreenshotIntervalMS = 1000;
 
 }
 
 namespace content {
 
-// Converts SkBitmap to grayscale and encodes to PNG data in a worker thread.
+// Encodes the A8 SkBitmap to grayscale PNG in a worker thread.
 class ScreenshotData : public base::RefCountedThreadSafe<ScreenshotData> {
  public:
   ScreenshotData() {
   }
 
   void EncodeScreenshot(const SkBitmap& bitmap, base::Closure callback) {
     if (!base::WorkerPool::PostTaskAndReply(FROM_HERE,
             base::Bind(&ScreenshotData::EncodeOnWorker,
                        this,
                        bitmap),
             callback,
             true)) {
       callback.Run();
     }
   }
 
   scoped_refptr<base::RefCountedBytes> data() const { return data_; }
 
  private:
   friend class base::RefCountedThreadSafe<ScreenshotData>;
   virtual ~ScreenshotData() {
   }
 
   void EncodeOnWorker(const SkBitmap& bitmap) {
+    DCHECK_EQ(bitmap.colorType(), kAlpha_8_SkColorType);
+    // Encode the A8 bitmap to grayscale PNG treating alpha as color intensity.
     std::vector<unsigned char> data;
-    // Paint |bitmap| to a kAlpha_8_SkColorType SkBitmap
-    SkBitmap a8Bitmap;
-    a8Bitmap.allocPixels(SkImageInfo::MakeA8(bitmap.width(), bitmap.height()));
-    SkCanvas canvas(a8Bitmap);
-    SkPaint paint;
-    SkColorFilter* filter = SkLumaColorFilter::Create();
-    paint.setColorFilter(filter);
-    filter->unref();
-    canvas.drawBitmap(bitmap, SkIntToScalar(0), SkIntToScalar(0), &paint);
-    // Encode the a8Bitmap to grayscale PNG treating alpha as color intensity
-    if (gfx::PNGCodec::EncodeA8SkBitmap(a8Bitmap, &data))
+    if (gfx::PNGCodec::EncodeA8SkBitmap(bitmap, &data))
       data_ = new base::RefCountedBytes(data);
   }
 
   scoped_refptr<base::RefCountedBytes> data_;
 
   DISALLOW_COPY_AND_ASSIGN(ScreenshotData);
 };
 
 NavigationEntryScreenshotManager::NavigationEntryScreenshotManager(
     NavigationControllerImpl* owner)
@@ skipping 46 matching lines @@
         owner_->GetEntryAtIndex(i)));
   }
   DCHECK_EQ(GetScreenshotCount(), 0);
 }
 
 void NavigationEntryScreenshotManager::TakeScreenshotImpl(
     RenderViewHost* host,
     NavigationEntryImpl* entry) {
   DCHECK(host && host->GetView());
   DCHECK(entry);
-  SkColorType preferred_format = host->PreferredReadbackFormat();
   host->CopyFromBackingStore(
       gfx::Rect(),
       host->GetView()->GetViewBounds().size(),
       base::Bind(&NavigationEntryScreenshotManager::OnScreenshotTaken,
                  screenshot_factory_.GetWeakPtr(),
                  entry->GetUniqueID()),
-      preferred_format);
+      kAlpha_8_SkColorType);
 }
 
 void NavigationEntryScreenshotManager::SetMinScreenshotIntervalMS(
     int interval_ms) {
   DCHECK_GE(interval_ms, 0);
   min_screenshot_interval_ms_ = interval_ms;
 }
 
 void NavigationEntryScreenshotManager::OnScreenshotTaken(int unique_id,
                                                      bool success,
@@ skipping 132 matching lines @@
         owner_->GetEntryAtIndex(forward));
     if (ClearScreenshot(entry))
       --screenshot_count;
     ++forward;
   }
   CHECK_GE(screenshot_count, 0);
   CHECK_LE(screenshot_count, kMaxScreenshots);
 }
 
 }  // namespace content