Improving GestureNav screenshotting performance - part 2 - GestureNav

Utilize the new gl_helper functionality to capture GestureNav screenshots
in grayscale, which drastically improves screencapture performance,
especially on hardware configurations with expensive RGBA readback.

Part 1: https://codereview.chromium.org/388953002/
Original review: https://codereview.chromium.org/384453002/

BUG=379983, 380779

Review URL: https://codereview.chromium.org/389683002

Cr-Commit-Position: refs/heads/master@{#291992}

content/browser/compositor/delegated_frame_host.cc

@@ -19,6 +19,9 @@
 #include "media/base/video_frame.h"
 #include "media/base/video_util.h"
 #include "skia/ext/image_operations.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/frame_time.h"
 
 namespace content {
@@ -136,7 +139,8 @@ void DelegatedFrameHost::CopyFromCompositingSurface(
     const base::Callback<void(bool, const SkBitmap&)>& callback,
     const SkColorType color_type) {
   // Only ARGB888 and RGB565 supported as of now.
-  bool format_support = ((color_type == kRGB_565_SkColorType) ||
+  bool format_support = ((color_type == kAlpha_8_SkColorType) ||
+                         (color_type == kRGB_565_SkColorType) ||
                          (color_type == kN32_SkColorType));
   DCHECK(format_support);
   if (!CanCopyToBitmap()) {
@@ -519,6 +523,7 @@ void DelegatedFrameHost::CopyFromCompositingSurfaceHasResult(
   }
 
   if (result->HasTexture()) {
+    // GPU-accelerated path
     PrepareTextureCopyOutputResult(dst_size_in_pixel, color_type,
                                    callback,
                                    result.Pass());
@@ -526,6 +531,7 @@ void DelegatedFrameHost::CopyFromCompositingSurfaceHasResult(
   }
 
   DCHECK(result->HasBitmap());
+  // Software path
   PrepareBitmapCopyOutputResult(dst_size_in_pixel, color_type, callback,
                                 result.Pass());
 }
@@ -604,7 +610,7 @@ void DelegatedFrameHost::PrepareBitmapCopyOutputResult(
     const SkColorType color_type,
     const base::Callback<void(bool, const SkBitmap&)>& callback,
     scoped_ptr<cc::CopyOutputResult> result) {
-  if (color_type != kN32_SkColorType) {
+  if (color_type != kN32_SkColorType && color_type != kAlpha_8_SkColorType) {
     NOTIMPLEMENTED();
     callback.Run(false, SkBitmap());
     return;
@@ -612,12 +618,41 @@ void DelegatedFrameHost::PrepareBitmapCopyOutputResult(
   DCHECK(result->HasBitmap());
   scoped_ptr<SkBitmap> source = result->TakeBitmap();
   DCHECK(source);
-  SkBitmap bitmap = skia::ImageOperations::Resize(
-      *source,
-      skia::ImageOperations::RESIZE_BEST,
-      dst_size_in_pixel.width(),
-      dst_size_in_pixel.height());
-  callback.Run(true, bitmap);
+  SkBitmap scaled_bitmap;
+  if (source->width() != dst_size_in_pixel.width() ||
+      source->height() != dst_size_in_pixel.height()) {
+    scaled_bitmap =
+        skia::ImageOperations::Resize(*source,
+                                      skia::ImageOperations::RESIZE_BEST,
+                                      dst_size_in_pixel.width(),
+                                      dst_size_in_pixel.height());
+  } else {
+    scaled_bitmap = *source;
+  }
+  if (color_type == kN32_SkColorType) {
+    DCHECK_EQ(scaled_bitmap.colorType(), kN32_SkColorType);
+    callback.Run(true, scaled_bitmap);
+    return;
+  }
+  DCHECK_EQ(color_type, kAlpha_8_SkColorType);
+  // The software path currently always returns N32 bitmap regardless of the
+  // |color_type| we ask for.
+  DCHECK_EQ(scaled_bitmap.colorType(), kN32_SkColorType);
+  // Paint |scaledBitmap| to alpha-only |grayscale_bitmap|.
+  SkBitmap grayscale_bitmap;
+  bool success = grayscale_bitmap.allocPixels(
+      SkImageInfo::MakeA8(scaled_bitmap.width(), scaled_bitmap.height()));
+  if (!success) {
+    callback.Run(false, SkBitmap());
+    return;
+  }
+  SkCanvas canvas(grayscale_bitmap);
+  SkPaint paint;
+  skia::RefPtr<SkColorFilter> filter =
+      skia::AdoptRef(SkLumaColorFilter::Create());
+  paint.setColorFilter(filter.get());
+  canvas.drawBitmap(scaled_bitmap, SkIntToScalar(0), SkIntToScalar(0), &paint);
+  callback.Run(true, grayscale_bitmap);
 }
 
 // static
@@ -636,6 +671,7 @@ void DelegatedFrameHost::ReturnSubscriberTexture(
     dfh->idle_frame_subscriber_textures_.push_back(subscriber_texture);
 }
 
+// static
 void DelegatedFrameHost::CopyFromCompositingSurfaceFinishedForVideo(
     base::WeakPtr<DelegatedFrameHost> dfh,
     const base::Callback<void(bool)>& callback,

content/browser/frame_host/navigation_controller_impl_unittest.cc

@@ -79,7 +79,8 @@ class MockScreenshotManager : public content::NavigationEntryScreenshotManager {
 
   void TakeScreenshotFor(content::NavigationEntryImpl* entry) {
     SkBitmap bitmap;
-    bitmap.allocN32Pixels(1, 1);
+    bitmap.allocPixels(SkImageInfo::Make(
+        1, 1, kAlpha_8_SkColorType, kPremul_SkAlphaType));
     bitmap.eraseARGB(0, 0, 0, 0);
     encoding_screenshot_in_progress_ = true;
     OnScreenshotTaken(entry->GetUniqueID(), true, bitmap);

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 {
@@ -27,7 +24,7 @@ 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() {
@@ -52,18 +49,10 @@ class ScreenshotData : public base::RefCountedThreadSafe<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);
   }
 
@@ -130,14 +119,13 @@ void NavigationEntryScreenshotManager::TakeScreenshotImpl(
     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(