Make ui::Snapshot asynchronous on Android, remove CompositeAndReadback.

ui/snapshot/snapshot_async.cc

Index: ui/snapshot/snapshot_async.cc
diff --git a/ui/snapshot/snapshot_async.cc b/ui/snapshot/snapshot_async.cc
new file mode 100644
index 0000000000000000000000000000000000000000..ab2aa5185e84d98b7391431b0b3c0be9ef485dd5
--- /dev/null
+++ b/ui/snapshot/snapshot_async.cc
@@ -0,0 +1,104 @@
+// Copyright (c) 2014 The Chromium Authors. All rights reserved.

[Ted C, 2014/05/14 01:13:18]

same here

[danakj, 2014/05/14 14:33:20]

Done.

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ui/snapshot/snapshot_async.h"
+
+#include "base/location.h"
+#include "base/memory/ref_counted.h"
+#include "base/numerics/safe_conversions.h"
+#include "base/task_runner_util.h"
+#include "cc/resources/single_release_callback.h"
+#include "skia/ext/image_operations.h"
+#include "third_party/skia/include/core/SkBitmap.h"
+#include "third_party/skia/include/core/SkPixelRef.h"
+#include "ui/gfx/codec/png_codec.h"
+#include "ui/gfx/image/image.h"
+#include "ui/gfx/image/image_skia.h"
+#include "ui/gfx/skbitmap_operations.h"
+
+namespace ui {
+
+namespace {
+
+void OnFrameScalingFinished(const GrabWindowSnapshotAsyncCallback& callback,
+                            const SkBitmap& scaled_bitmap) {
+  callback.Run(gfx::Image(gfx::ImageSkia::CreateFrom1xBitmap(scaled_bitmap)));
+}
+
+SkBitmap ScaleBitmap(const SkBitmap& input_bitmap,
+                     const gfx::Size& target_size) {
+  return skia::ImageOperations::Resize(input_bitmap,
+                                       skia::ImageOperations::RESIZE_GOOD,
+                                       target_size.width(),
+                                       target_size.height(),
+                                       static_cast<SkBitmap::Allocator*>(NULL));
+}
+
+scoped_refptr<base::RefCountedBytes> EncodeBitmap(const SkBitmap& bitmap) {
+  scoped_refptr<base::RefCountedBytes> png_data(new base::RefCountedBytes);
+  unsigned char* pixels =

[sky, 2014/05/13 23:43:13]

Don't you need to lockPixels before accessing them?

[danakj, 2014/05/14 14:33:20]

We should, I'll add that.

+      reinterpret_cast<unsigned char*>(bitmap.pixelRef()->pixels());

[sky, 2014/05/13 23:43:13]

Might pixelRef return NULL?

[danakj, 2014/05/14 14:33:20]

No, the bitmap here always has content in it returned from the compositor. It
would return a NULL bitmap instead if the readback didn't happen.

I changed it to bitmap.getPixels() anyway since I want to use SkAutoLockPixels
which is on the bitmap.

+#if SK_A32_SHIFT == 24 && SK_R32_SHIFT == 16 && SK_G32_SHIFT == 8
+  gfx::PNGCodec::ColorFormat kColorFormat = gfx::PNGCodec::FORMAT_BGRA;
+#elif SK_A32_SHIFT == 24 && SK_B32_SHIFT == 16 && SK_G32_SHIFT == 8
+  gfx::PNGCodec::ColorFormat kColorFormat = gfx::PNGCodec::FORMAT_RGBA;
+#else
+#error Unknown color format
+#endif
+  if (!gfx::PNGCodec::Encode(pixels,
+                             kColorFormat,
+                             gfx::Size(bitmap.width(), bitmap.height()),
+                             base::checked_cast<int>(bitmap.rowBytes()),
+                             true,
+                             std::vector<gfx::PNGCodec::Comment>(),
+                             &png_data->data())) {
+    return scoped_refptr<base::RefCountedBytes>();
+  }
+  return png_data;
+}
+
+}  // namespace
+
+void SnapshotAsync::ScaleCopyOutputResult(
+    const GrabWindowSnapshotAsyncCallback& callback,
+    const gfx::Size& target_size,
+    scoped_refptr<base::TaskRunner> background_task_runner,
+    scoped_ptr<cc::CopyOutputResult> result) {
+  if (result->IsEmpty()) {
+    callback.Run(gfx::Image());
+    return;
+  }
+
+  // TODO(sergeyu): Potentially images can be scaled on GPU before reading it
+  // from GPU. Image scaling is implemented in content::GlHelper, but it's can't
+  // be used here because it's not in content/public. Move the scaling code
+  // somewhere so that it can be reused here.
+  base::PostTaskAndReplyWithResult(
+      background_task_runner,
+      FROM_HERE,
+      base::Bind(ScaleBitmap, *result->TakeBitmap(), target_size),
+      base::Bind(&OnFrameScalingFinished, callback));
+}
+
+void SnapshotAsync::EncodeCopyOutputResult(
+    const GrabWindowSnapshotAsyncPNGCallback& callback,
+    scoped_refptr<base::TaskRunner> background_task_runner,
+    scoped_ptr<cc::CopyOutputResult> result) {
+  if (result->IsEmpty()) {
+    callback.Run(scoped_refptr<base::RefCountedBytes>());
+    return;
+  }
+
+  // TODO(sergeyu): Potentially images can be scaled on GPU before reading it
+  // from GPU. Image scaling is implemented in content::GlHelper, but it's can't
+  // be used here because it's not in content/public. Move the scaling code
+  // somewhere so that it can be reused here.
+  base::PostTaskAndReplyWithResult(
+      background_task_runner,
+      FROM_HERE,
+      base::Bind(EncodeBitmap, *result->TakeBitmap()),
+      callback);
+}
+
+}  // namespace ui