Revert of Remove code used by --disable-delegated-renderer on Mac

content/browser/renderer_host/compositing_iosurface_mac.mm

Index: content/browser/renderer_host/compositing_iosurface_mac.mm
diff --git a/content/browser/renderer_host/compositing_iosurface_mac.mm b/content/browser/renderer_host/compositing_iosurface_mac.mm
index 701239999da34873d3a9a7a95584a29f8d9dfd95..35c5a35f2b585a759757a8f0a297dc42ece33c4b 100644
--- a/content/browser/renderer_host/compositing_iosurface_mac.mm
+++ b/content/browser/renderer_host/compositing_iosurface_mac.mm
@@ -17,6 +17,8 @@
 #include "base/threading/platform_thread.h"
 #include "content/browser/gpu/gpu_data_manager_impl.h"
 #include "content/browser/renderer_host/compositing_iosurface_context_mac.h"
+#include "content/browser/renderer_host/compositing_iosurface_shader_programs_mac.h"
+#include "content/browser/renderer_host/compositing_iosurface_transformer_mac.h"
 #include "content/browser/renderer_host/render_widget_host_impl.h"
 #include "content/browser/renderer_host/render_widget_host_view_mac.h"
 #include "content/common/content_constants_internal.h"
@@ -43,6 +45,176 @@
 #endif
 
 namespace content {
+namespace {
+
+// How many times to test if asynchronous copy has completed.
+// This value is chosen such that we allow at most 1 second to finish a copy.
+const int kFinishCopyRetryCycles = 100;
+
+// Time in milliseconds to allow asynchronous copy to finish.
+// This value is shorter than 16ms such that copy can complete within a vsync.
+const int kFinishCopyPollingPeriodMs = 10;
+
+bool HasAppleFenceExtension() {
+  static bool initialized_has_fence = false;
+  static bool has_fence = false;
+
+  if (!initialized_has_fence) {
+    has_fence =
+        strstr(reinterpret_cast<const char*>(glGetString(GL_EXTENSIONS)),
+               "GL_APPLE_fence") != NULL;
+    initialized_has_fence = true;
+  }
+  return has_fence;
+}
+
+bool HasPixelBufferObjectExtension() {
+  static bool initialized_has_pbo = false;
+  static bool has_pbo = false;
+
+  if (!initialized_has_pbo) {
+    has_pbo =
+        strstr(reinterpret_cast<const char*>(glGetString(GL_EXTENSIONS)),
+               "GL_ARB_pixel_buffer_object") != NULL;
+    initialized_has_pbo = true;
+  }
+  return has_pbo;
+}
+
+// Helper function to reverse the argument order.  Also takes ownership of
+// |bitmap_output| for the life of the binding.
+void ReverseArgumentOrder(
+    const base::Callback<void(bool, const SkBitmap&)>& callback,
+    scoped_ptr<SkBitmap> bitmap_output, bool success) {
+  callback.Run(success, *bitmap_output);
+}
+
+// Called during an async GPU readback with a pointer to the pixel buffer.  In
+// the snapshot path, we just memcpy the data into our output bitmap since the
+// width, height, and stride should all be equal.
+bool MapBufferToSkBitmap(const SkBitmap* output, const void* buf, int ignored) {
+  TRACE_EVENT0("browser", "MapBufferToSkBitmap");
+
+  if (buf) {
+    SkAutoLockPixels output_lock(*output);
+    memcpy(output->getPixels(), buf, output->getSize());
+  }
+  return buf != NULL;
+}
+
+// Copies tightly-packed scanlines from |buf| to |region_in_frame| in the given
+// |target| VideoFrame's |plane|.  Assumption: |buf|'s width is
+// |region_in_frame.width()| and its stride is always in 4-byte alignment.
+//
+// TODO(miu): Refactor by moving this function into media/video_util.
+// http://crbug.com/219779
+bool MapBufferToVideoFrame(
+    const scoped_refptr<media::VideoFrame>& target,
+    const gfx::Rect& region_in_frame,
+    const void* buf,
+    int plane) {
+  COMPILE_ASSERT(media::VideoFrame::kYPlane == 0, VideoFrame_kYPlane_mismatch);
+  COMPILE_ASSERT(media::VideoFrame::kUPlane == 1, VideoFrame_kUPlane_mismatch);
+  COMPILE_ASSERT(media::VideoFrame::kVPlane == 2, VideoFrame_kVPlane_mismatch);
+
+  TRACE_EVENT1("browser", "MapBufferToVideoFrame", "plane", plane);
+
+  // Apply black-out in the regions surrounding the view area (for
+  // letterboxing/pillarboxing).  Only do this once, since this is performed on
+  // all planes in the VideoFrame here.
+  if (plane == 0)
+    media::LetterboxYUV(target.get(), region_in_frame);
+
+  if (buf) {
+    int packed_width = region_in_frame.width();
+    int packed_height = region_in_frame.height();
+    // For planes 1 and 2, the width and height are 1/2 size (rounded up).
+    if (plane > 0) {
+      packed_width = (packed_width + 1) / 2;
+      packed_height = (packed_height + 1) / 2;
+    }
+    const uint8* src = reinterpret_cast<const uint8*>(buf);
+    const int src_stride = (packed_width % 4 == 0 ?
+                                packed_width :
+                                (packed_width + 4 - (packed_width % 4)));
+    const uint8* const src_end = src + packed_height * src_stride;
+
+    // Calculate starting offset and stride into the destination buffer.
+    const int dst_stride = target->stride(plane);
+    uint8* dst = target->data(plane);
+    if (plane == 0)
+      dst += (region_in_frame.y() * dst_stride) + region_in_frame.x();
+    else
+      dst += (region_in_frame.y() / 2 * dst_stride) + (region_in_frame.x() / 2);
+
+    // Copy each row, accounting for strides in the source and destination.
+    for (; src < src_end; src += src_stride, dst += dst_stride)
+      memcpy(dst, src, packed_width);
+  }
+  return buf != NULL;
+}
+
+}  // namespace
+
+CompositingIOSurfaceMac::CopyContext::CopyContext(
+    const scoped_refptr<CompositingIOSurfaceContext>& context)
+  : transformer(new CompositingIOSurfaceTransformer(
+        GL_TEXTURE_RECTANGLE_ARB, true, context->shader_program_cache())),
+    output_readback_format(GL_BGRA),
+    num_outputs(0),
+    fence(0),
+    cycles_elapsed(0) {
+  memset(output_textures, 0, sizeof(output_textures));
+  memset(frame_buffers, 0, sizeof(frame_buffers));
+  memset(pixel_buffers, 0, sizeof(pixel_buffers));
+}
+
+CompositingIOSurfaceMac::CopyContext::~CopyContext() {
+  DCHECK_EQ(frame_buffers[0], 0u) << "Failed to call ReleaseCachedGLObjects().";
+}
+
+void CompositingIOSurfaceMac::CopyContext::ReleaseCachedGLObjects() {
+  // No outstanding callbacks should be pending.
+  DCHECK(map_buffer_callback.is_null());
+  DCHECK(done_callback.is_null());
+
+  // For an asynchronous read-back, there are more objects to delete:
+  if (fence) {
+    glDeleteBuffers(arraysize(pixel_buffers), pixel_buffers); CHECK_GL_ERROR();
+    memset(pixel_buffers, 0, sizeof(pixel_buffers));
+    glDeleteFencesAPPLE(1, &fence); CHECK_GL_ERROR();
+    fence = 0;
+  }
+
+  glDeleteFramebuffersEXT(arraysize(frame_buffers), frame_buffers);
+  CHECK_GL_ERROR();
+  memset(frame_buffers, 0, sizeof(frame_buffers));
+
+  // Note: |output_textures| are owned by the transformer.
+  if (transformer)
+    transformer->ReleaseCachedGLObjects();
+}
+
+void CompositingIOSurfaceMac::CopyContext::PrepareReadbackFramebuffers() {
+  for (int i = 0; i < num_outputs; ++i) {
+    if (!frame_buffers[i]) {
+      glGenFramebuffersEXT(1, &frame_buffers[i]); CHECK_GL_ERROR();
+    }
+  }
+}
+
+void CompositingIOSurfaceMac::CopyContext::PrepareForAsynchronousReadback() {
+  PrepareReadbackFramebuffers();
+  if (!fence) {
+    glGenFencesAPPLE(1, &fence); CHECK_GL_ERROR();
+  }
+  for (int i = 0; i < num_outputs; ++i) {
+    if (!pixel_buffers[i]) {
+      glGenBuffersARB(1, &pixel_buffers[i]); CHECK_GL_ERROR();
+    }
+  }
+}
+
 
 // static
 scoped_refptr<CompositingIOSurfaceMac> CompositingIOSurfaceMac::Create() {
@@ -63,6 +235,13 @@
       io_surface_handle_(0),
       scale_factor_(1.f),
       texture_(0),
+      finish_copy_timer_(
+          FROM_HERE,
+          base::TimeDelta::FromMilliseconds(kFinishCopyPollingPeriodMs),
+          base::Bind(&CompositingIOSurfaceMac::CheckIfAllCopiesAreFinished,
+                     base::Unretained(this),
+                     false),
+          true),
       gl_error_(GL_NO_ERROR),
       eviction_queue_iterator_(eviction_queue_.Get().end()),
       eviction_has_been_drawn_since_updated_(false) {
@@ -70,9 +249,11 @@
 }
 
 CompositingIOSurfaceMac::~CompositingIOSurfaceMac() {
+  FailAllCopies();
   {
     gfx::ScopedCGLSetCurrentContext scoped_set_current_context(
         offscreen_context_->cgl_context());
+    DestroyAllCopyContextsWithinContext();
     UnrefIOSurfaceWithContextCurrent();
   }
   offscreen_context_ = NULL;
@@ -131,18 +312,19 @@
   glDisable(GL_DEPTH_TEST);
   glDisable(GL_BLEND);
 
-  glColor4f(1, 1, 1, 1);
   if (has_io_surface) {
-    glEnable(GL_TEXTURE_RECTANGLE_ARB);
+    drawing_context->shader_program_cache()->UseBlitProgram();
+    glActiveTexture(GL_TEXTURE0);
     glBindTexture(GL_TEXTURE_RECTANGLE_ARB, texture_);
+
     DrawQuad(quad);
-    glBindTexture(GL_TEXTURE_RECTANGLE_ARB, 0);
-    glDisable(GL_TEXTURE_RECTANGLE_ARB);
-    CHECK_AND_SAVE_GL_ERROR();
+
+    glBindTexture(GL_TEXTURE_RECTANGLE_ARB, 0); CHECK_AND_SAVE_GL_ERROR();
 
     // Fill the resize gutters with white.
     if (window_rect.width() > dip_io_surface_size_.width() ||
         window_rect.height() > dip_io_surface_size_.height()) {
+      drawing_context->shader_program_cache()->UseSolidWhiteProgram();
       SurfaceQuad filler_quad;
       if (window_rect.width() > dip_io_surface_size_.width()) {
         // Draw right-side gutter down to the bottom of the window.
@@ -160,11 +342,12 @@
     }
 
     // Workaround for issue 158469. Issue a dummy draw call with texture_ not
-    // bound to a texture, in order to shake all references to the IOSurface out
-    // of the driver.
+    // bound to blit_rgb_sampler_location_, in order to shake all references
+    // to the IOSurface out of the driver.
     glBegin(GL_TRIANGLES);
     glEnd();
-    CHECK_AND_SAVE_GL_ERROR();
+
+    glUseProgram(0); CHECK_AND_SAVE_GL_ERROR();
   } else {
     // Should match the clear color of RenderWidgetHostViewMac.
     glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
@@ -195,6 +378,70 @@
 
   eviction_has_been_drawn_since_updated_ = true;
   return result;
+}
+
+void CompositingIOSurfaceMac::CopyTo(
+      const gfx::Rect& src_pixel_subrect,
+      const gfx::Size& dst_pixel_size,
+      const base::Callback<void(bool, const SkBitmap&)>& callback) {
+  scoped_ptr<SkBitmap> output(new SkBitmap());
+  if (!output->allocN32Pixels(
+          dst_pixel_size.width(), dst_pixel_size.height(), true)) {
+    DLOG(ERROR) << "Failed to allocate SkBitmap pixels!";
+    callback.Run(false, *output);
+    return;
+  }
+  DCHECK_EQ(output->rowBytesAsPixels(), dst_pixel_size.width())
+      << "Stride is required to be equal to width for GPU readback.";
+
+  base::Closure copy_done_callback;
+  {
+    gfx::ScopedCGLSetCurrentContext scoped_set_current_context(
+        offscreen_context_->cgl_context());
+    copy_done_callback = CopyToSelectedOutputWithinContext(
+        src_pixel_subrect, gfx::Rect(dst_pixel_size), false,
+        output.get(), NULL,
+        base::Bind(&ReverseArgumentOrder, callback, base::Passed(&output)));
+  }
+  if (!copy_done_callback.is_null())
+    copy_done_callback.Run();
+}
+
+void CompositingIOSurfaceMac::CopyToVideoFrame(
+    const gfx::Rect& src_pixel_subrect,
+    const scoped_refptr<media::VideoFrame>& target,
+    const base::Callback<void(bool)>& callback) {
+  base::Closure copy_done_callback;
+  {
+    gfx::ScopedCGLSetCurrentContext scoped_set_current_context(
+        offscreen_context_->cgl_context());
+    copy_done_callback = CopyToVideoFrameWithinContext(
+        src_pixel_subrect, false, target, callback);
+  }
+  if (!copy_done_callback.is_null())
+    copy_done_callback.Run();
+}
+
+base::Closure CompositingIOSurfaceMac::CopyToVideoFrameWithinContext(
+    const gfx::Rect& src_pixel_subrect,
+    bool called_within_draw,
+    const scoped_refptr<media::VideoFrame>& target,
+    const base::Callback<void(bool)>& callback) {
+  gfx::Rect region_in_frame = media::ComputeLetterboxRegion(
+      gfx::Rect(target->coded_size()), src_pixel_subrect.size());
+  // Make coordinates and sizes even because we letterbox in YUV space right
+  // now (see CopyRGBToVideoFrame). They need to be even for the UV samples to
+  // line up correctly.
+  region_in_frame = gfx::Rect(region_in_frame.x() & ~1,
+                              region_in_frame.y() & ~1,
+                              region_in_frame.width() & ~1,
+                              region_in_frame.height() & ~1);
+  DCHECK_LE(region_in_frame.right(), target->coded_size().width());
+  DCHECK_LE(region_in_frame.bottom(), target->coded_size().height());
+
+  return CopyToSelectedOutputWithinContext(
+      src_pixel_subrect, region_in_frame, called_within_draw,
+      NULL, target, callback);
 }
 
 bool CompositingIOSurfaceMac::MapIOSurfaceToTextureWithContextCurrent(
@@ -302,8 +549,346 @@
   EvictionMarkEvicted();
 }
 
+bool CompositingIOSurfaceMac::IsAsynchronousReadbackSupported() {
+  if (!HasAppleFenceExtension() && HasPixelBufferObjectExtension())
+    return false;
+  if (GpuDataManagerImpl::GetInstance()->IsDriverBugWorkaroundActive(
+          gpu::DISABLE_ASYNC_READPIXELS)) {
+    return false;
+  }
+  return true;
+}
+
 bool CompositingIOSurfaceMac::HasBeenPoisoned() const {
   return offscreen_context_->HasBeenPoisoned();
+}
+
+base::Closure CompositingIOSurfaceMac::CopyToSelectedOutputWithinContext(
+    const gfx::Rect& src_pixel_subrect,
+    const gfx::Rect& dst_pixel_rect,
+    bool called_within_draw,
+    const SkBitmap* bitmap_output,
+    const scoped_refptr<media::VideoFrame>& video_frame_output,
+    const base::Callback<void(bool)>& done_callback) {
+  DCHECK_NE(bitmap_output != NULL, video_frame_output.get() != NULL);
+  DCHECK(!done_callback.is_null());
+
+  // SWIZZLE_RGBA_FOR_ASYNC_READPIXELS workaround: Fall-back to synchronous
+  // readback for SkBitmap output since the Blit shader program doesn't support
+  // switchable output formats.
+  const bool require_sync_copy_for_workaround = bitmap_output &&
+      offscreen_context_->shader_program_cache()->rgb_to_yv12_output_format() ==
+          GL_RGBA;
+  const bool async_copy = !require_sync_copy_for_workaround &&
+      IsAsynchronousReadbackSupported();
+  TRACE_EVENT2(
+      "browser", "CompositingIOSurfaceMac::CopyToSelectedOutputWithinContext",
+      "output", bitmap_output ? "SkBitmap (ARGB)" : "VideoFrame (YV12)",
+      "async_readback", async_copy);
+
+  const gfx::Rect src_rect = IntersectWithIOSurface(src_pixel_subrect);
+  if (src_rect.IsEmpty() || dst_pixel_rect.IsEmpty())
+    return base::Bind(done_callback, false);
+
+  CopyContext* copy_context;
+  if (copy_context_pool_.empty()) {
+    // Limit the maximum number of simultaneous copies to two.  Rationale:
+    // Really, only one should ever be in-progress at a time, as we should
+    // depend on the speed of the hardware to rate-limit the copying naturally.
+    // In the asynchronous read-back case, the one currently in-flight copy is
+    // highly likely to have finished by this point (i.e., it's just waiting for
+    // us to make a glMapBuffer() call).  Therefore, we allow a second copy to
+    // be started here.
+    if (copy_requests_.size() >= 2)
+      return base::Bind(done_callback, false);
+    copy_context = new CopyContext(offscreen_context_);
+  } else {
+    copy_context = copy_context_pool_.back();
+    copy_context_pool_.pop_back();
+  }
+
+  if (!HasIOSurface())
+    return base::Bind(done_callback, false);
+
+  // Send transform commands to the GPU.
+  copy_context->num_outputs = 0;
+  if (bitmap_output) {
+    if (copy_context->transformer->ResizeBilinear(
+            texture_, src_rect, dst_pixel_rect.size(),
+            &copy_context->output_textures[0])) {
+      copy_context->output_readback_format = GL_BGRA;
+      copy_context->num_outputs = 1;
+      copy_context->output_texture_sizes[0] = dst_pixel_rect.size();
+    }
+  } else {
+    if (copy_context->transformer->TransformRGBToYV12(
+            texture_, src_rect, dst_pixel_rect.size(),
+            &copy_context->output_textures[0],
+            &copy_context->output_textures[1],
+            &copy_context->output_textures[2],
+            &copy_context->output_texture_sizes[0],
+            &copy_context->output_texture_sizes[1])) {
+      copy_context->output_readback_format =
+          offscreen_context_->shader_program_cache()->
+              rgb_to_yv12_output_format();
+      copy_context->num_outputs = 3;
+      copy_context->output_texture_sizes[2] =
+          copy_context->output_texture_sizes[1];
+    }
+  }
+  if (!copy_context->num_outputs)
+    return base::Bind(done_callback, false);
+
+  // In the asynchronous case, issue commands to the GPU and return a null
+  // closure here.  In the synchronous case, perform a blocking readback and
+  // return a callback to be run outside the CGL context to indicate success.
+  if (async_copy) {
+    copy_context->done_callback = done_callback;
+    AsynchronousReadbackForCopy(
+        dst_pixel_rect, called_within_draw, copy_context, bitmap_output,
+        video_frame_output);
+    copy_requests_.push_back(copy_context);
+    if (!finish_copy_timer_.IsRunning())
+      finish_copy_timer_.Reset();
+    return base::Closure();
+  } else {
+    const bool success = SynchronousReadbackForCopy(
+        dst_pixel_rect, copy_context, bitmap_output, video_frame_output);
+    return base::Bind(done_callback, success);
+  }
+}
+
+void CompositingIOSurfaceMac::AsynchronousReadbackForCopy(
+    const gfx::Rect& dst_pixel_rect,
+    bool called_within_draw,
+    CopyContext* copy_context,
+    const SkBitmap* bitmap_output,
+    const scoped_refptr<media::VideoFrame>& video_frame_output) {
+  copy_context->PrepareForAsynchronousReadback();
+
+  // Copy the textures to their corresponding PBO.
+  for (int i = 0; i < copy_context->num_outputs; ++i) {
+    TRACE_EVENT1(
+        "browser", "CompositingIOSurfaceMac::AsynchronousReadbackForCopy",
+        "plane", i);
+
+    // Attach the output texture to the FBO.
+    glBindFramebufferEXT(
+        GL_READ_FRAMEBUFFER_EXT, copy_context->frame_buffers[i]);
+    glFramebufferTexture2DEXT(
+        GL_READ_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT,
+        GL_TEXTURE_RECTANGLE_ARB, copy_context->output_textures[i], 0);
+    DCHECK(glCheckFramebufferStatusEXT(GL_READ_FRAMEBUFFER_EXT) ==
+               GL_FRAMEBUFFER_COMPLETE_EXT);
+
+    // Create a PBO and issue an asynchronous read-back.
+    glBindBufferARB(GL_PIXEL_PACK_BUFFER_ARB, copy_context->pixel_buffers[i]);
+    CHECK_AND_SAVE_GL_ERROR();
+    glBufferDataARB(GL_PIXEL_PACK_BUFFER_ARB,
+                    copy_context->output_texture_sizes[i].GetArea() * 4,
+                    NULL, GL_STREAM_READ_ARB);
+    CHECK_AND_SAVE_GL_ERROR();
+    glReadPixels(0, 0,
+                 copy_context->output_texture_sizes[i].width(),
+                 copy_context->output_texture_sizes[i].height(),
+                 copy_context->output_readback_format,
+                 GL_UNSIGNED_INT_8_8_8_8_REV, 0);
+    CHECK_AND_SAVE_GL_ERROR();
+  }
+
+  glBindBufferARB(GL_PIXEL_PACK_BUFFER_ARB, 0); CHECK_AND_SAVE_GL_ERROR();
+  glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0); CHECK_AND_SAVE_GL_ERROR();
+
+  glSetFenceAPPLE(copy_context->fence); CHECK_GL_ERROR();
+  copy_context->cycles_elapsed = 0;
+
+  // When this asynchronous copy happens in a draw operaton there is no need
+  // to explicitly flush because there will be a swap buffer and this flush
+  // hurts performance.
+  if (!called_within_draw) {
+    glFlush(); CHECK_AND_SAVE_GL_ERROR();
+  }
+
+  copy_context->map_buffer_callback = bitmap_output ?
+      base::Bind(&MapBufferToSkBitmap, bitmap_output) :
+      base::Bind(&MapBufferToVideoFrame, video_frame_output, dst_pixel_rect);
+}
+
+void CompositingIOSurfaceMac::CheckIfAllCopiesAreFinished(
+    bool block_until_finished) {
+  if (copy_requests_.empty())
+    return;
+
+  std::vector<base::Closure> done_callbacks;
+  {
+    gfx::ScopedCGLSetCurrentContext scoped_set_current_context(
+        offscreen_context_->cgl_context());
+    CheckIfAllCopiesAreFinishedWithinContext(
+        block_until_finished, &done_callbacks);
+  }
+  for (size_t i = 0; i < done_callbacks.size(); ++i)
+    done_callbacks[i].Run();
+}
+
+void CompositingIOSurfaceMac::CheckIfAllCopiesAreFinishedWithinContext(
+    bool block_until_finished,
+    std::vector<base::Closure>* done_callbacks) {
+  while (!copy_requests_.empty()) {
+    CopyContext* const copy_context = copy_requests_.front();
+
+    if (copy_context->fence && !glTestFenceAPPLE(copy_context->fence)) {
+      CHECK_AND_SAVE_GL_ERROR();
+      // Doing a glFinishFenceAPPLE can cause transparent window flashes when
+      // switching tabs, so only do it when required.
+      if (block_until_finished) {
+        glFinishFenceAPPLE(copy_context->fence);
+        CHECK_AND_SAVE_GL_ERROR();
+      } else if (copy_context->cycles_elapsed < kFinishCopyRetryCycles) {
+        ++copy_context->cycles_elapsed;
+        // This copy has not completed there is no need to test subsequent
+        // requests.
+        break;
+      }
+    }
+    CHECK_AND_SAVE_GL_ERROR();
+
+    bool success = true;
+    for (int i = 0; success && i < copy_context->num_outputs; ++i) {
+      TRACE_EVENT1(
+        "browser",
+        "CompositingIOSurfaceMac::CheckIfAllCopiesAreFinishedWithinContext",
+        "plane", i);
+
+      glBindBufferARB(GL_PIXEL_PACK_BUFFER_ARB, copy_context->pixel_buffers[i]);
+      CHECK_AND_SAVE_GL_ERROR();
+
+      void* buf = glMapBuffer(GL_PIXEL_PACK_BUFFER_ARB, GL_READ_ONLY_ARB);
+      CHECK_AND_SAVE_GL_ERROR();
+      success &= copy_context->map_buffer_callback.Run(buf, i);
+      glUnmapBufferARB(GL_PIXEL_PACK_BUFFER_ARB); CHECK_AND_SAVE_GL_ERROR();
+    }
+    copy_context->map_buffer_callback.Reset();
+    glBindBufferARB(GL_PIXEL_PACK_BUFFER_ARB, 0); CHECK_AND_SAVE_GL_ERROR();
+
+    copy_requests_.pop_front();
+    done_callbacks->push_back(base::Bind(copy_context->done_callback, success));
+    copy_context->done_callback.Reset();
+    copy_context_pool_.push_back(copy_context);
+  }
+  if (copy_requests_.empty())
+    finish_copy_timer_.Stop();
+
+  CHECK(copy_requests_.empty() || !block_until_finished);
+}
+
+bool CompositingIOSurfaceMac::SynchronousReadbackForCopy(
+    const gfx::Rect& dst_pixel_rect,
+    CopyContext* copy_context,
+    const SkBitmap* bitmap_output,
+    const scoped_refptr<media::VideoFrame>& video_frame_output) {
+  bool success = true;
+  copy_context->PrepareReadbackFramebuffers();
+  for (int i = 0; i < copy_context->num_outputs; ++i) {
+    TRACE_EVENT1(
+        "browser", "CompositingIOSurfaceMac::SynchronousReadbackForCopy",
+        "plane", i);
+
+    // Attach the output texture to the FBO.
+    glBindFramebufferEXT(
+        GL_READ_FRAMEBUFFER_EXT, copy_context->frame_buffers[i]);
+    glFramebufferTexture2DEXT(
+        GL_READ_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT,
+        GL_TEXTURE_RECTANGLE_ARB, copy_context->output_textures[i], 0);
+    DCHECK(glCheckFramebufferStatusEXT(GL_READ_FRAMEBUFFER_EXT) ==
+               GL_FRAMEBUFFER_COMPLETE_EXT);
+
+    // Blocking read-back of pixels from textures.
+    void* buf;
+    // When data must be transferred into a VideoFrame one scanline at a time,
+    // it is necessary to allocate a separate buffer for glReadPixels() that can
+    // be populated one-shot.
+    //
+    // TODO(miu): Don't keep allocating/deleting this buffer for every frame.
+    // Keep it cached, allocated on first use.
+    scoped_ptr<uint32[]> temp_readback_buffer;
+    if (bitmap_output) {
+      // The entire SkBitmap is populated, never a region within.  So, read the
+      // texture directly into the bitmap's pixel memory.
+      buf = bitmap_output->getPixels();
+    } else {
+      // Optimization: If the VideoFrame is letterboxed (not pillarboxed), and
+      // its stride is equal to the stride of the data being read back, then
+      // readback directly into the VideoFrame's buffer to save a round of
+      // memcpy'ing.
+      //
+      // TODO(miu): Move these calculations into VideoFrame (need a CalcOffset()
+      // method).  http://crbug.com/219779
+      const int src_stride = copy_context->output_texture_sizes[i].width() * 4;
+      const int dst_stride = video_frame_output->stride(i);
+      if (src_stride == dst_stride && dst_pixel_rect.x() == 0) {
+        const int y_offset = dst_pixel_rect.y() / (i == 0 ? 1 : 2);
+        buf = video_frame_output->data(i) + y_offset * dst_stride;
+      } else {
+        // Create and readback into a temporary buffer because the data must be
+        // transferred to VideoFrame's pixel memory one scanline at a time.
+        temp_readback_buffer.reset(
+            new uint32[copy_context->output_texture_sizes[i].GetArea()]);
+        buf = temp_readback_buffer.get();
+      }
+    }
+    glReadPixels(0, 0,
+                 copy_context->output_texture_sizes[i].width(),
+                 copy_context->output_texture_sizes[i].height(),
+                 copy_context->output_readback_format,
+                 GL_UNSIGNED_INT_8_8_8_8_REV, buf);
+    CHECK_AND_SAVE_GL_ERROR();
+    if (video_frame_output.get()) {
+      if (!temp_readback_buffer) {
+        // Apply letterbox black-out around view region.
+        media::LetterboxYUV(video_frame_output.get(), dst_pixel_rect);
+      } else {
+        // Copy from temporary buffer and fully render the VideoFrame.
+        success &= MapBufferToVideoFrame(video_frame_output, dst_pixel_rect,
+                                         temp_readback_buffer.get(), i);
+      }
+    }
+  }
+
+  glBindFramebufferEXT(GL_READ_FRAMEBUFFER_EXT, 0); CHECK_AND_SAVE_GL_ERROR();
+  copy_context_pool_.push_back(copy_context);
+  return success;
+}
+
+void CompositingIOSurfaceMac::FailAllCopies() {
+  for (size_t i = 0; i < copy_requests_.size(); ++i) {
+    copy_requests_[i]->map_buffer_callback.Reset();
+
+    base::Callback<void(bool)>& done_callback =
+        copy_requests_[i]->done_callback;
+    if (!done_callback.is_null()) {
+      done_callback.Run(false);
+      done_callback.Reset();
+    }
+  }
+}
+
+void CompositingIOSurfaceMac::DestroyAllCopyContextsWithinContext() {
+  // Move all in-flight copies, if any, back into the pool.  Then, destroy all
+  // the CopyContexts in the pool.
+  copy_context_pool_.insert(copy_context_pool_.end(),
+                            copy_requests_.begin(), copy_requests_.end());
+  copy_requests_.clear();
+  while (!copy_context_pool_.empty()) {
+    scoped_ptr<CopyContext> copy_context(copy_context_pool_.back());
+    copy_context_pool_.pop_back();
+    copy_context->ReleaseCachedGLObjects();
+  }
+}
+
+gfx::Rect CompositingIOSurfaceMac::IntersectWithIOSurface(
+    const gfx::Rect& rect) const {
+  return gfx::IntersectRects(rect,
+      gfx::ToEnclosingRect(gfx::Rect(pixel_io_surface_size_)));
 }
 
 GLenum CompositingIOSurfaceMac::GetAndSaveGLError() {
@@ -361,6 +946,10 @@
     if (!surface->eviction_has_been_drawn_since_updated_)
       continue;
 
+    // Don't evict anything with pending copy requests.
+    if (!surface->copy_requests_.empty())
+      continue;
+
     // Evict the surface.
     surface->UnrefIOSurface();
   }