wip: Improving GestureNav screenshotting performance

content/browser/frame_host/navigation_entry_screenshot_manager.cc

Index: content/browser/frame_host/navigation_entry_screenshot_manager.cc
diff --git a/content/browser/frame_host/navigation_entry_screenshot_manager.cc b/content/browser/frame_host/navigation_entry_screenshot_manager.cc
index 1e476827703d617b9759edfe17c9d3d564ed2a66..4959ba8692830bd7491b356078090358257fff51 100644
--- a/content/browser/frame_host/navigation_entry_screenshot_manager.cc
+++ b/content/browser/frame_host/navigation_entry_screenshot_manager.cc
@@ -13,9 +13,6 @@
 #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 {
@@ -53,21 +50,8 @@ class ScreenshotData : public base::RefCountedThreadSafe<ScreenshotData> {
 
   void EncodeOnWorker(const SkBitmap& bitmap) {
     std::vector<unsigned char> data;
-    // Paint |bitmap| to a kA8_Config SkBitmap
-    SkBitmap a8Bitmap;
-    a8Bitmap.setConfig(SkBitmap::kA8_Config,
-                       bitmap.width(),
-                       bitmap.height(),
-                       0);
-    a8Bitmap.allocPixels();
-    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))
+    // Encode the A8 bitmap to grayscale PNG treating alpha as color intensity.

[danakj, 2014/07/10 19:13:02]

you can dcheck the bitmap config here if you like? might be nice

[mfomitchev, 2014/07/11 19:46:07]

Done. I did it in the other place because the stack trace from that error would
be more useful (since this one is run on WorkerPool), but yeah, I guess that's
not a great reason.

+    if (gfx::PNGCodec::EncodeA8SkBitmap(bitmap, &data))
       data_ = new base::RefCountedBytes(data);
   }
 
@@ -134,14 +118,13 @@ void NavigationEntryScreenshotManager::TakeScreenshotImpl(
     NavigationEntryImpl* entry) {
   DCHECK(host && host->GetView());
   DCHECK(entry);
-  SkBitmap::Config preferred_format = host->PreferredReadbackFormat();
   host->CopyFromBackingStore(
       gfx::Rect(),
       host->GetView()->GetViewBounds().size(),
       base::Bind(&NavigationEntryScreenshotManager::OnScreenshotTaken,
                  screenshot_factory_.GetWeakPtr(),
                  entry->GetUniqueID()),
-      preferred_format);
+     SkBitmap::kA8_Config);
 }
 
 void NavigationEntryScreenshotManager::SetMinScreenshotIntervalMS(
@@ -153,6 +136,8 @@ void NavigationEntryScreenshotManager::SetMinScreenshotIntervalMS(
 void NavigationEntryScreenshotManager::OnScreenshotTaken(int unique_id,
                                                      bool success,
                                                      const SkBitmap& bitmap) {
+  LOG(ERROR) << "OnScreenshotTaken";
+
   NavigationEntryImpl* entry = NULL;
   int entry_count = owner_->GetEntryCount();
   for (int i = 0; i < entry_count; ++i) {
@@ -174,6 +159,9 @@ void NavigationEntryScreenshotManager::OnScreenshotTaken(int unique_id,
     return;
   }
 
+  CHECK(bitmap.getConfig() == SkBitmap::kA8_Config)

[danakj, 2014/07/10 19:13:02]

DCHECK_EQ, then you don't need the extra << either as it'll print out both

[mfomitchev, 2014/07/11 19:46:07]

Done.

+      << "Incorrect screenshot format: " << bitmap.getConfig();
+
   scoped_refptr<ScreenshotData> screenshot = new ScreenshotData();
   screenshot->EncodeScreenshot(
       bitmap,