Perform glReadPixels with PBOs in the gpu, if PBOs are available.

Make GL_ASYNC_READ_PIXELS_COMPLETED_CHROMIUM wait for readpixel transfers.
PLEASE NOTE: glMapBuffer does not wait for the readpixels transfer to complete anymore.
Nobody is currently relying on that behaviour.
Update gl_helper.cc and gl_renderer.cc to use queries.

This CL is the same as https://codereview.chromium.org/16831004/, which was submitted and reverted because it seemed to cause
 OutOfProcessPPAPITest.Graphics3D failures on XP.

Since I don't have an XP box and there are no XP trybots I can't seem to reproduce the problem. Also, this particular test is flaky and has had problems even after my CL was reverted.  Thus, I'm going to try to submit it again, and if that breaks OutOfProcessPPAPITest.Graphics3D again, I apologize in advance.



BUG=249925

Review URL: https://chromiumcodereview.appspot.com/18555006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@209873 0039d316-1c4b-4281-b951-d872f2087c98

19 files changed, 323 insertions, 99 deletions

diff --git a/gpu/GLES2/gl2extchromium.h b/gpu/GLES2/gl2extchromium.h
index 2568074..433242c 100644
--- a/gpu/GLES2/gl2extchromium.h
+++ b/gpu/GLES2/gl2extchromium.h
@@ -339,6 +339,9 @@ typedef void (GL_APIENTRYP PFNGLBINDUNIFORMLOCATIONCHROMIUMPROC) (
 #ifndef GL_ASYNC_PIXEL_TRANSFERS_COMPLETED_CHROMIUM
 #define GL_ASYNC_PIXEL_TRANSFERS_COMPLETED_CHROMIUM 0x84F5
 #endif
+#ifndef GL_ASYNC_READ_PIXELS_COMPLETED_CHROMIUM
+#define GL_ASYNC_READ_PIXELS_COMPLETED_CHROMIUM 0x84F6
+#endif
 #endif  /* GL_CHROMIUM_async_pixel_transfers */
 
 /* GL_CHROMIUM_copy_texture */
diff --git a/gpu/command_buffer/build_gles2_cmd_buffer.py b/gpu/command_buffer/build_gles2_cmd_buffer.py
index d3fa65a..af49a93 100755
--- a/gpu/command_buffer/build_gles2_cmd_buffer.py
+++ b/gpu/command_buffer/build_gles2_cmd_buffer.py
@@ -826,6 +826,7 @@ _ENUM_LISTS = {
       'GL_COMMANDS_ISSUED_CHROMIUM',
       'GL_LATENCY_QUERY_CHROMIUM',
       'GL_ASYNC_PIXEL_TRANSFERS_COMPLETED_CHROMIUM',
+      'GL_ASYNC_READ_PIXELS_COMPLETED_CHROMIUM',
     ],
   },
   'RenderBufferParameter': {
@@ -1901,7 +1902,8 @@ _FUNCTION_INFO = {
         'GLint x, GLint y, GLsizei width, GLsizei height, '
         'GLenumReadPixelFormat format, GLenumReadPixelType type, '
         'uint32 pixels_shm_id, uint32 pixels_shm_offset, '
-        'uint32 result_shm_id, uint32 result_shm_offset',
+        'uint32 result_shm_id, uint32 result_shm_offset, '
+        'GLboolean async',
     'result': ['uint32'],
     'defer_reads': True,
   },
diff --git a/gpu/command_buffer/client/gles2_cmd_helper_autogen.h b/gpu/command_buffer/client/gles2_cmd_helper_autogen.h
index a290365..9c2898e 100644
--- a/gpu/command_buffer/client/gles2_cmd_helper_autogen.h
+++ b/gpu/command_buffer/client/gles2_cmd_helper_autogen.h
@@ -923,12 +923,12 @@
   void ReadPixels(
       GLint x, GLint y, GLsizei width, GLsizei height, GLenum format,
       GLenum type, uint32 pixels_shm_id, uint32 pixels_shm_offset,
-      uint32 result_shm_id, uint32 result_shm_offset) {
+      uint32 result_shm_id, uint32 result_shm_offset, GLboolean async) {
     gles2::cmds::ReadPixels* c = GetCmdSpace<gles2::cmds::ReadPixels>();
     if (c) {
       c->Init(
           x, y, width, height, format, type, pixels_shm_id, pixels_shm_offset,
-          result_shm_id, result_shm_offset);
+          result_shm_id, result_shm_offset, async);
     }
   }
 
diff --git a/gpu/command_buffer/client/gles2_implementation.cc b/gpu/command_buffer/client/gles2_implementation.cc
index fbc92d5..57dd4e0 100644
--- a/gpu/command_buffer/client/gles2_implementation.cc
+++ b/gpu/command_buffer/client/gles2_implementation.cc
@@ -2236,8 +2236,7 @@ void GLES2Implementation::ReadPixels(
     if (buffer && buffer->shm_id() != -1) {
       helper_->ReadPixels(xoffset, yoffset, width, height, format, type,
                           buffer->shm_id(), buffer->shm_offset(),
-                          0, 0);
-      buffer->set_transfer_ready_token(helper_->InsertToken());
+                          0, 0, true);
       CheckGLError();
     }
     return;
@@ -2269,7 +2268,8 @@ void GLES2Implementation::ReadPixels(
     helper_->ReadPixels(
         xoffset, yoffset, width, num_rows, format, type,
         buffer.shm_id(), buffer.offset(),
-        GetResultShmId(), GetResultShmOffset());
+        GetResultShmId(), GetResultShmOffset(),
+        false);
     WaitForCmd();
     if (*result != 0) {
       // when doing a y-flip we have to iterate through top-to-bottom chunks
@@ -3175,36 +3175,31 @@ void GLES2Implementation::DeleteQueriesEXTHelper(
     return;
   }
   // When you delete a query you can't mark its memory as unused until it's
-  // completed.
+  // either completed, or deleted in the gpu process.
   // Note: If you don't do this you won't mess up the service but you will mess
   // up yourself.
 
-  // TODO(gman): Consider making this faster by putting pending quereies
-  // on some queue to be removed when they are finished.
   bool query_pending = false;
   for (GLsizei ii = 0; ii < n; ++ii) {
     QueryTracker::Query* query = query_tracker_->GetQuery(queries[ii]);
-    if (query && query->Pending()) {
+    if (query && !query->CheckResultsAvailable(helper_)) {
       query_pending = true;
       break;
     }
   }
 
+  helper_->DeleteQueriesEXTImmediate(n, queries);
+
   if (query_pending) {
+    // This should make sure that the GPU process have deleted the queries
+    // and given up any claim on the shared memory that goes along with
+    // those queries so that we can safely re-use the shared memory.
     WaitForCmd();
   }
 
   for (GLsizei ii = 0; ii < n; ++ii) {
-    QueryTracker::Query* query = query_tracker_->GetQuery(queries[ii]);
-    if (query && query->Pending()) {
-      if (!query->CheckResultsAvailable(helper_)) {
-        // Should only get here on context lost.
-        MustBeContextLost();
-      }
-    }
     query_tracker_->RemoveQuery(queries[ii], helper_->IsContextLost());
   }
-  helper_->DeleteQueriesEXTImmediate(n, queries);
 }
 
 // TODO(gman): Remove this. Queries are not shared resources.
diff --git a/gpu/command_buffer/client/gles2_implementation_unittest.cc b/gpu/command_buffer/client/gles2_implementation_unittest.cc
index 7208425..bdbde8f 100644
--- a/gpu/command_buffer/client/gles2_implementation_unittest.cc
+++ b/gpu/command_buffer/client/gles2_implementation_unittest.cc
@@ -1438,11 +1438,12 @@ TEST_F(GLES2ImplementationTest, ReadPixels2Reads) {
   Cmds expected;
   expected.read1.Init(
       0, 0, kWidth, kHeight / 2, kFormat, kType,
-      mem1.id, mem1.offset, result1.id, result1.offset);
+      mem1.id, mem1.offset, result1.id, result1.offset,
+      false);
   expected.set_token1.Init(GetNextToken());
   expected.read2.Init(
       0, kHeight / 2, kWidth, kHeight / 2, kFormat, kType,
-      mem2.id, mem2.offset, result2.id, result2.offset);
+      mem2.id, mem2.offset, result2.id, result2.offset, false);
   expected.set_token2.Init(GetNextToken());
   scoped_ptr<int8[]> buffer(new int8[kWidth * kHeight * kBytesPerPixel]);
 
@@ -1474,7 +1475,7 @@ TEST_F(GLES2ImplementationTest, ReadPixelsBadFormatType) {
   Cmds expected;
   expected.read.Init(
       0, 0, kWidth, kHeight, kFormat, kType,
-      mem1.id, mem1.offset, result1.id, result1.offset);
+      mem1.id, mem1.offset, result1.id, result1.offset, false);
   expected.set_token.Init(GetNextToken());
   scoped_ptr<int8[]> buffer(new int8[kWidth * kHeight * kBytesPerPixel]);
 
diff --git a/gpu/command_buffer/client/query_tracker.cc b/gpu/command_buffer/client/query_tracker.cc
index 76ebf72..7cd1ae8 100644
--- a/gpu/command_buffer/client/query_tracker.cc
+++ b/gpu/command_buffer/client/query_tracker.cc
@@ -113,9 +113,7 @@ void QueryTracker::Query::Begin(GLES2Implementation* gl) {
       gl->helper()->BeginQueryEXT(target(), id(), shm_id(), shm_offset());
       break;
     case GL_ASYNC_PIXEL_TRANSFERS_COMPLETED_CHROMIUM:
-      // tell service about id, shared memory and count
-      gl->helper()->BeginQueryEXT(target(), id(), shm_id(), shm_offset());
-      break;
+    case GL_ASYNC_READ_PIXELS_COMPLETED_CHROMIUM:
     default:
       // tell service about id, shared memory and count
       gl->helper()->BeginQueryEXT(target(), id(), shm_id(), shm_offset());
@@ -165,8 +163,7 @@ bool QueryTracker::Query::CheckResultsAvailable(
                              static_cast<uint64>(0xFFFFFFFFL));
           break;
         case GL_ASYNC_PIXEL_TRANSFERS_COMPLETED_CHROMIUM:
-          result_ = info_.sync->result;
-          break;
+        case GL_ASYNC_READ_PIXELS_COMPLETED_CHROMIUM:
         default:
           result_ = info_.sync->result;
           break;
diff --git a/gpu/command_buffer/common/gles2_cmd_format_autogen.h b/gpu/command_buffer/common/gles2_cmd_format_autogen.h
index 12fc743..504c445 100644
--- a/gpu/command_buffer/common/gles2_cmd_format_autogen.h
+++ b/gpu/command_buffer/common/gles2_cmd_format_autogen.h
@@ -4887,7 +4887,7 @@ struct ReadPixels {
   void Init(
       GLint _x, GLint _y, GLsizei _width, GLsizei _height, GLenum _format,
       GLenum _type, uint32 _pixels_shm_id, uint32 _pixels_shm_offset,
-      uint32 _result_shm_id, uint32 _result_shm_offset) {
+      uint32 _result_shm_id, uint32 _result_shm_offset, GLboolean _async) {
     SetHeader();
     x = _x;
     y = _y;
@@ -4899,17 +4899,18 @@ struct ReadPixels {
     pixels_shm_offset = _pixels_shm_offset;
     result_shm_id = _result_shm_id;
     result_shm_offset = _result_shm_offset;
+    async = _async;
   }
 
   void* Set(
       void* cmd, GLint _x, GLint _y, GLsizei _width, GLsizei _height,
       GLenum _format, GLenum _type, uint32 _pixels_shm_id,
       uint32 _pixels_shm_offset, uint32 _result_shm_id,
-      uint32 _result_shm_offset) {
+      uint32 _result_shm_offset, GLboolean _async) {
     static_cast<ValueType*>(
         cmd)->Init(
             _x, _y, _width, _height, _format, _type, _pixels_shm_id,
-            _pixels_shm_offset, _result_shm_id, _result_shm_offset);
+            _pixels_shm_offset, _result_shm_id, _result_shm_offset, _async);
     return NextCmdAddress<ValueType>(cmd);
   }
 
@@ -4924,10 +4925,11 @@ struct ReadPixels {
   uint32 pixels_shm_offset;
   uint32 result_shm_id;
   uint32 result_shm_offset;
+  uint32 async;
 };
 
-COMPILE_ASSERT(sizeof(ReadPixels) == 44,
-               Sizeof_ReadPixels_is_not_44);
+COMPILE_ASSERT(sizeof(ReadPixels) == 48,
+               Sizeof_ReadPixels_is_not_48);
 COMPILE_ASSERT(offsetof(ReadPixels, header) == 0,
                OffsetOf_ReadPixels_header_not_0);
 COMPILE_ASSERT(offsetof(ReadPixels, x) == 4,
@@ -4950,6 +4952,8 @@ COMPILE_ASSERT(offsetof(ReadPixels, result_shm_id) == 36,
                OffsetOf_ReadPixels_result_shm_id_not_36);
 COMPILE_ASSERT(offsetof(ReadPixels, result_shm_offset) == 40,
                OffsetOf_ReadPixels_result_shm_offset_not_40);
+COMPILE_ASSERT(offsetof(ReadPixels, async) == 44,
+               OffsetOf_ReadPixels_async_not_44);
 
 struct ReleaseShaderCompiler {
   typedef ReleaseShaderCompiler ValueType;
diff --git a/gpu/command_buffer/common/gles2_cmd_format_test_autogen.h b/gpu/command_buffer/common/gles2_cmd_format_test_autogen.h
index b23b569..8bb1ec0 100644
--- a/gpu/command_buffer/common/gles2_cmd_format_test_autogen.h
+++ b/gpu/command_buffer/common/gles2_cmd_format_test_autogen.h
@@ -1803,7 +1803,8 @@ TEST_F(GLES2FormatTest, ReadPixels) {
       static_cast<uint32>(17),
       static_cast<uint32>(18),
       static_cast<uint32>(19),
-      static_cast<uint32>(20));
+      static_cast<uint32>(20),
+      static_cast<GLboolean>(21));
   EXPECT_EQ(static_cast<uint32>(cmds::ReadPixels::kCmdId),
             cmd.header.command);
   EXPECT_EQ(sizeof(cmd), cmd.header.size * 4u);
@@ -1817,6 +1818,7 @@ TEST_F(GLES2FormatTest, ReadPixels) {
   EXPECT_EQ(static_cast<uint32>(18), cmd.pixels_shm_offset);
   EXPECT_EQ(static_cast<uint32>(19), cmd.result_shm_id);
   EXPECT_EQ(static_cast<uint32>(20), cmd.result_shm_offset);
+  EXPECT_EQ(static_cast<GLboolean>(21), cmd.async);
   CheckBytesWrittenMatchesExpectedSize(
       next_cmd, sizeof(cmd));
 }
diff --git a/gpu/command_buffer/common/gles2_cmd_utils_implementation_autogen.h b/gpu/command_buffer/common/gles2_cmd_utils_implementation_autogen.h
index 36975dd..3c3fb33 100644
--- a/gpu/command_buffer/common/gles2_cmd_utils_implementation_autogen.h
+++ b/gpu/command_buffer/common/gles2_cmd_utils_implementation_autogen.h
@@ -86,6 +86,7 @@ static GLES2Util::EnumToString enum_to_string_table[] = {
   { 0x2601, "GL_LINEAR", },
   { 0x8C03, "GL_COMPRESSED_RGBA_PVRTC_2BPPV1_IMG", },
   { 0x9242, "GL_UNPACK_UNPREMULTIPLY_ALPHA_CHROMIUM", },
+  { 0x88BA, "GL_READ_WRITE", },
   { 0x88BB, "GL_BUFFER_ACCESS_OES", },
   { 0x88BC, "GL_BUFFER_MAPPED_OES", },
   { 0x88BD, "GL_BUFFER_MAP_POINTER_OES", },
@@ -227,7 +228,7 @@ static GLES2Util::EnumToString enum_to_string_table[] = {
   { 0x84F5, "GL_ASYNC_PIXEL_TRANSFERS_COMPLETED_CHROMIUM", },
   { 0x882A, "GL_DRAW_BUFFER5_NV", },
   { 0x80AA, "GL_SAMPLE_COVERAGE_VALUE", },
-  { 0x84F6, "GL_TEXTURE_BINDING_RECTANGLE_ARB", },
+  { 0x84F6, "GL_ASYNC_READ_PIXELS_COMPLETED_CHROMIUM", },
   { 0x80AB, "GL_SAMPLE_COVERAGE_INVERT", },
   { 0x8FC4, "GL_SHADER_BINARY_VIV", },
   { 0x882B, "GL_DRAW_BUFFER6_NV", },
@@ -1079,6 +1080,8 @@ std::string GLES2Util::GetStringQueryTarget(uint32 value) {
     { GL_LATENCY_QUERY_CHROMIUM, "GL_LATENCY_QUERY_CHROMIUM" },
     { GL_ASYNC_PIXEL_TRANSFERS_COMPLETED_CHROMIUM,
     "GL_ASYNC_PIXEL_TRANSFERS_COMPLETED_CHROMIUM" },
+    { GL_ASYNC_READ_PIXELS_COMPLETED_CHROMIUM,
+    "GL_ASYNC_READ_PIXELS_COMPLETED_CHROMIUM" },
   };
   return GLES2Util::GetQualifiedEnumString(
       string_table, arraysize(string_table), value);
diff --git a/gpu/command_buffer/service/feature_info.cc b/gpu/command_buffer/service/feature_info.cc
index 5d95848..396311c 100644
--- a/gpu/command_buffer/service/feature_info.cc
+++ b/gpu/command_buffer/service/feature_info.cc
@@ -117,7 +117,8 @@ FeatureInfo::FeatureFlags::FeatureFlags()
       enable_shader_name_hashing(false),
       enable_samplers(false),
       ext_draw_buffers(false),
-      ext_frag_depth(false) {
+      ext_frag_depth(false),
+      use_async_readpixels(false) {
 }
 
 FeatureInfo::Workarounds::Workarounds() :
@@ -623,6 +624,16 @@ void FeatureInfo::AddFeatures(const CommandLine& command_line) {
     feature_flags_.ext_frag_depth = true;
   }
 
+  bool ui_gl_fence_works =
+      extensions.Contains("GL_NV_fence") ||
+      extensions.Contains("GL_ARB_sync");
+
+  if (ui_gl_fence_works &&
+      extensions.Contains("GL_ARB_pixel_buffer_object") &&
+      !workarounds_.disable_async_readpixels) {
+    feature_flags_.use_async_readpixels = true;
+  }
+
   if (!disallowed_features_.swap_buffer_complete_callback)
     AddExtensionString("GL_CHROMIUM_swapbuffers_complete_callback");
 
diff --git a/gpu/command_buffer/service/feature_info.h b/gpu/command_buffer/service/feature_info.h
index 3754a3c..87abfba 100644
--- a/gpu/command_buffer/service/feature_info.h
+++ b/gpu/command_buffer/service/feature_info.h
@@ -45,6 +45,7 @@ class GPU_EXPORT FeatureInfo : public base::RefCounted<FeatureInfo> {
     bool enable_samplers;
     bool ext_draw_buffers;
     bool ext_frag_depth;
+    bool use_async_readpixels;
   };
 
   struct Workarounds {
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.cc b/gpu/command_buffer/service/gles2_cmd_decoder.cc
index 5b10fff..afb6b14 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -59,6 +59,7 @@
 #include "gpu/command_buffer/service/vertex_array_manager.h"
 #include "gpu/command_buffer/service/vertex_attrib_manager.h"
 #include "ui/gl/gl_bindings.h"
+#include "ui/gl/gl_fence.h"
 #include "ui/gl/gl_image.h"
 #include "ui/gl/gl_implementation.h"
 #include "ui/gl/gl_surface.h"
@@ -477,6 +478,19 @@ class BackFramebuffer {
   DISALLOW_COPY_AND_ASSIGN(BackFramebuffer);
 };
 
+struct FenceCallback {
+  explicit FenceCallback()
+      : fence(gfx::GLFence::Create()) {
+    DCHECK(fence);
+  }
+  void AddCallback(base::Closure cb) {
+    callbacks.push_back(cb);
+  }
+  std::vector<base::Closure> callbacks;
+  scoped_ptr<gfx::GLFence> fence;
+};
+
+
 // }  // anonymous namespace.
 
 bool GLES2Decoder::GetServiceTextureId(uint32 client_texture_id,
@@ -587,6 +601,8 @@ class GLES2DecoderImpl : public GLES2Decoder {
   virtual bool HasMoreIdleWork() OVERRIDE;
   virtual void PerformIdleWork() OVERRIDE;
 
+  virtual void WaitForReadPixels(base::Closure callback) OVERRIDE;
+
   virtual void SetResizeCallback(
       const base::Callback<void(gfx::Size, float)>& callback) OVERRIDE;
 
@@ -1560,6 +1576,9 @@ class GLES2DecoderImpl : public GLES2Decoder {
            surface_->DeferDraws();
   }
 
+  void ProcessPendingReadPixels();
+  void FinishReadPixels(const cmds::ReadPixels& c, GLuint buffer);
+
   void ForceCompileShaderIfPending(Shader* shader);
 
   // Generate a member function prototype for each command in an automated and
@@ -1728,6 +1747,8 @@ class GLES2DecoderImpl : public GLES2Decoder {
 
   scoped_ptr<GPUTracer> gpu_tracer_;
 
+  std::queue<linked_ptr<FenceCallback> > pending_readpixel_fences_;
+
   DISALLOW_COPY_AND_ASSIGN(GLES2DecoderImpl);
 };
 
@@ -2808,6 +2829,7 @@ bool GLES2DecoderImpl::MakeCurrent() {
 }
 
 void GLES2DecoderImpl::ProcessFinishedAsyncTransfers() {
+  ProcessPendingReadPixels();
   if (engine() && query_manager_.get())
     query_manager_->ProcessPendingTransferQueries();
 
@@ -3536,6 +3558,7 @@ bool GLES2DecoderImpl::CreateShaderHelper(GLenum type, GLuint client_id) {
 
 void GLES2DecoderImpl::DoFinish() {
   glFinish();
+  ProcessPendingReadPixels();
   ProcessPendingQueries();
 }
 
@@ -6698,6 +6721,96 @@ error::Error GLES2DecoderImpl::HandleVertexAttribDivisorANGLE(
   return error::kNoError;
 }
 
+void GLES2DecoderImpl::FinishReadPixels(
+    const cmds::ReadPixels& c,
+    GLuint buffer) {
+  TRACE_EVENT0("gpu", "GLES2DecoderImpl::FinishReadPixels");
+  GLsizei width = c.width;
+  GLsizei height = c.height;
+  GLenum format = c.format;
+  GLenum type = c.type;
+  typedef cmds::ReadPixels::Result Result;
+  uint32 pixels_size;
+  Result* result = NULL;
+  if (c.result_shm_id != 0) {
+    result = GetSharedMemoryAs<Result*>(
+        c.result_shm_id, c.result_shm_offset, sizeof(*result));
+    if (!result) {
+      if (buffer != 0) {
+        glDeleteBuffersARB(1, &buffer);
+      }
+      return;
+    }
+  }
+  GLES2Util::ComputeImageDataSizes(
+      width, height, format, type, state_.pack_alignment, &pixels_size,
+      NULL, NULL);
+  void* pixels = GetSharedMemoryAs<void*>(
+      c.pixels_shm_id, c.pixels_shm_offset, pixels_size);
+  if (!pixels) {
+    if (buffer != 0) {
+      glDeleteBuffersARB(1, &buffer);
+    }
+    return;
+  }
+
+  if (buffer != 0) {
+    glBindBuffer(GL_PIXEL_PACK_BUFFER_ARB, buffer);
+    void* data = glMapBuffer(GL_PIXEL_PACK_BUFFER_ARB, GL_READ_ONLY);
+    memcpy(pixels, data, pixels_size);
+    // GL_PIXEL_PACK_BUFFER_ARB is currently unused, so we don't
+    // have to restore the state.
+    glUnmapBuffer(GL_PIXEL_PACK_BUFFER_ARB);
+    glBindBuffer(GL_PIXEL_PACK_BUFFER_ARB, 0);
+    glDeleteBuffersARB(1, &buffer);
+  }
+
+  if (result != NULL) {
+    *result = true;
+  }
+
+  GLenum read_format = GetBoundReadFrameBufferInternalFormat();
+  uint32 channels_exist = GLES2Util::GetChannelsForFormat(read_format);
+  if ((channels_exist & 0x0008) == 0 &&
+      workarounds().clear_alpha_in_readpixels) {
+    // Set the alpha to 255 because some drivers are buggy in this regard.
+    uint32 temp_size;
+
+    uint32 unpadded_row_size;
+    uint32 padded_row_size;
+    if (!GLES2Util::ComputeImageDataSizes(
+            width, 2, format, type, state_.pack_alignment, &temp_size,
+            &unpadded_row_size, &padded_row_size)) {
+      return;
+    }
+    // NOTE: Assumes the type is GL_UNSIGNED_BYTE which was true at the time
+    // of this implementation.
+    if (type != GL_UNSIGNED_BYTE) {
+      return;
+    }
+    switch (format) {
+      case GL_RGBA:
+      case GL_BGRA_EXT:
+      case GL_ALPHA: {
+        int offset = (format == GL_ALPHA) ? 0 : 3;
+        int step = (format == GL_ALPHA) ? 1 : 4;
+        uint8* dst = static_cast<uint8*>(pixels) + offset;
+        for (GLint yy = 0; yy < height; ++yy) {
+          uint8* end = dst + unpadded_row_size;
+          for (uint8* d = dst; d < end; d += step) {
+            *d = 255;
+          }
+          dst += padded_row_size;
+        }
+        break;
+      }
+      default:
+        break;
+    }
+  }
+}
+
+
 error::Error GLES2DecoderImpl::HandleReadPixels(
     uint32 immediate_data_size, const cmds::ReadPixels& c) {
   if (ShouldDeferReads())
@@ -6708,6 +6821,7 @@ error::Error GLES2DecoderImpl::HandleReadPixels(
   GLsizei height = c.height;
   GLenum format = c.format;
   GLenum type = c.type;
+  GLboolean async = c.async;
   if (width < 0 || height < 0) {
     LOCAL_SET_GL_ERROR(GL_INVALID_VALUE, "glReadPixels", "dimensions < 0");
     return error::kNoError;
@@ -6807,6 +6921,25 @@ error::Error GLES2DecoderImpl::HandleReadPixels(
       dst += padded_row_size;
     }
   } else {
+    if (async && features().use_async_readpixels) {
+      GLuint buffer;
+      glGenBuffersARB(1, &buffer);
+      glBindBuffer(GL_PIXEL_PACK_BUFFER_ARB, buffer);
+      glBufferData(GL_PIXEL_PACK_BUFFER_ARB, pixels_size, NULL, GL_STREAM_READ);
+      GLenum error = glGetError();
+      if (error == GL_NO_ERROR) {
+        glReadPixels(x, y, width, height, format, type, 0);
+        pending_readpixel_fences_.push(linked_ptr<FenceCallback>(
+            new FenceCallback()));
+        WaitForReadPixels(base::Bind(
+            &GLES2DecoderImpl::FinishReadPixels,
+            base::internal::SupportsWeakPtrBase::StaticAsWeakPtr
+            <GLES2DecoderImpl>(this),
+            c, buffer));
+        glBindBuffer(GL_PIXEL_PACK_BUFFER_ARB, 0);
+        return error::kNoError;
+      }
+    }
     glReadPixels(x, y, width, height, format, type, pixels);
   }
   GLenum error = LOCAL_PEEK_GL_ERROR("glReadPixels");
@@ -6814,51 +6947,7 @@ error::Error GLES2DecoderImpl::HandleReadPixels(
     if (result != NULL) {
       *result = true;
     }
-
-    GLenum read_format = GetBoundReadFrameBufferInternalFormat();
-    uint32 channels_exist = GLES2Util::GetChannelsForFormat(read_format);
-    if ((channels_exist & 0x0008) == 0 &&
-        workarounds().clear_alpha_in_readpixels) {
-      // Set the alpha to 255 because some drivers are buggy in this regard.
-      uint32 temp_size;
-
-      uint32 unpadded_row_size;
-      uint32 padded_row_size;
-      if (!GLES2Util::ComputeImageDataSizes(
-          width, 2, format, type, state_.pack_alignment, &temp_size,
-          &unpadded_row_size, &padded_row_size)) {
-        LOCAL_SET_GL_ERROR(
-            GL_INVALID_VALUE, "glReadPixels", "dimensions out of range");
-        return error::kNoError;
-      }
-      // NOTE: Assumes the type is GL_UNSIGNED_BYTE which was true at the time
-      // of this implementation.
-      if (type != GL_UNSIGNED_BYTE) {
-        LOCAL_SET_GL_ERROR(
-            GL_INVALID_OPERATION, "glReadPixels",
-            "unsupported readPixel format");
-        return error::kNoError;
-      }
-      switch (format) {
-        case GL_RGBA:
-        case GL_BGRA_EXT:
-        case GL_ALPHA: {
-          int offset = (format == GL_ALPHA) ? 0 : 3;
-          int step = (format == GL_ALPHA) ? 1 : 4;
-          uint8* dst = static_cast<uint8*>(pixels) + offset;
-          for (GLint yy = 0; yy < height; ++yy) {
-            uint8* end = dst + unpadded_row_size;
-            for (uint8* d = dst; d < end; d += step) {
-              *d = 255;
-            }
-            dst += padded_row_size;
-          }
-          break;
-        }
-        default:
-          break;
-      }
-    }
+    FinishReadPixels(c, 0);
   }
 
   return error::kNoError;
@@ -9093,11 +9182,35 @@ bool GLES2DecoderImpl::ProcessPendingQueries() {
   return query_manager_->HavePendingQueries();
 }
 
+// Note that if there are no pending readpixels right now,
+// this function will call the callback immediately.
+void GLES2DecoderImpl::WaitForReadPixels(base::Closure callback) {
+  if (features().use_async_readpixels && !pending_readpixel_fences_.empty()) {
+    pending_readpixel_fences_.back()->callbacks.push_back(callback);
+  } else {
+    callback.Run();
+  }
+}
+
+void GLES2DecoderImpl::ProcessPendingReadPixels() {
+  while (!pending_readpixel_fences_.empty() &&
+         pending_readpixel_fences_.front()->fence->HasCompleted()) {
+    std::vector<base::Closure> callbacks =
+        pending_readpixel_fences_.front()->callbacks;
+    pending_readpixel_fences_.pop();
+    for (size_t i = 0; i < callbacks.size(); i++) {
+      callbacks[i].Run();
+    }
+  }
+}
+
 bool GLES2DecoderImpl::HasMoreIdleWork() {
-  return async_pixel_transfer_manager_->NeedsProcessMorePendingTransfers();
+  return !pending_readpixel_fences_.empty() ||
+      async_pixel_transfer_manager_->NeedsProcessMorePendingTransfers();
 }
 
 void GLES2DecoderImpl::PerformIdleWork() {
+  ProcessPendingReadPixels();
   if (!async_pixel_transfer_manager_->NeedsProcessMorePendingTransfers())
     return;
   async_pixel_transfer_manager_->ProcessMorePendingTransfers();
@@ -9115,6 +9228,7 @@ error::Error GLES2DecoderImpl::HandleBeginQueryEXT(
     case GL_COMMANDS_ISSUED_CHROMIUM:
     case GL_LATENCY_QUERY_CHROMIUM:
     case GL_ASYNC_PIXEL_TRANSFERS_COMPLETED_CHROMIUM:
+    case GL_ASYNC_READ_PIXELS_COMPLETED_CHROMIUM:
     case GL_GET_ERROR_QUERY_CHROMIUM:
       break;
     default:
@@ -9127,6 +9241,8 @@ error::Error GLES2DecoderImpl::HandleBeginQueryEXT(
       break;
   }
 
+  // TODO(hubbe): Make it possible to have one query per type running at the
+  // same time.
   if (state_.current_query.get()) {
     LOCAL_SET_GL_ERROR(
         GL_INVALID_OPERATION, "glBeginQueryEXT", "query already in progress");
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.h b/gpu/command_buffer/service/gles2_cmd_decoder.h
index 4f66a62..57445c7 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.h
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.h
@@ -213,6 +213,7 @@ class GPU_EXPORT GLES2Decoder : public base::SupportsWeakPtr<GLES2Decoder>,
   virtual void SetWaitSyncPointCallback(
       const WaitSyncPointCallback& callback) = 0;
 
+  virtual void WaitForReadPixels(base::Closure callback) = 0;
   virtual uint32 GetTextureUploadCount() = 0;
   virtual base::TimeDelta GetTotalTextureUploadTime() = 0;
   virtual base::TimeDelta GetTotalProcessingCommandsTime() = 0;
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder_mock.h b/gpu/command_buffer/service/gles2_cmd_decoder_mock.h
index 5fe0600..e6c497f 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder_mock.h
+++ b/gpu/command_buffer/service/gles2_cmd_decoder_mock.h
@@ -102,6 +102,8 @@ class MockGLES2Decoder : public GLES2Decoder {
                void(const ShaderCacheCallback& callback));
   MOCK_METHOD1(SetWaitSyncPointCallback,
                void(const WaitSyncPointCallback& callback));
+  MOCK_METHOD1(WaitForReadPixels,
+               void(base::Closure callback));
   MOCK_METHOD0(GetTextureUploadCount, uint32());
   MOCK_METHOD0(GetTotalTextureUploadTime, base::TimeDelta());
   MOCK_METHOD0(GetTotalProcessingCommandsTime, base::TimeDelta());
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder_unittest.cc b/gpu/command_buffer/service/gles2_cmd_decoder_unittest.cc
index 09ed184..b426286 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder_unittest.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder_unittest.cc
@@ -2316,7 +2316,8 @@ void GLES2DecoderTest::CheckReadPixelsOutOfRange(
   cmd.Init(in_read_x, in_read_y, in_read_width, in_read_height,
            kFormat, GL_UNSIGNED_BYTE,
            pixels_shm_id, pixels_shm_offset,
-           result_shm_id, result_shm_offset);
+           result_shm_id, result_shm_offset,
+           false);
   EXPECT_EQ(error::kNoError, ExecuteCmd(cmd));
 
   GLint unpadded_row_size = emu.ComputeImageDataSize(in_read_width, 1);
@@ -2393,7 +2394,8 @@ TEST_F(GLES2DecoderTest, ReadPixels) {
   ReadPixels cmd;
   cmd.Init(0, 0, kWidth, kHeight, GL_RGB, GL_UNSIGNED_BYTE,
            pixels_shm_id, pixels_shm_offset,
-           result_shm_id, result_shm_offset);
+           result_shm_id, result_shm_offset,
+           false);
   EXPECT_EQ(error::kNoError, ExecuteCmd(cmd));
   for (GLint yy = 0; yy < kHeight; ++yy) {
     EXPECT_TRUE(emu.CompareRowSegment(
@@ -2440,7 +2442,8 @@ TEST_F(GLES2DecoderRGBBackbufferTest, ReadPixelsNoAlphaBackbuffer) {
   ReadPixels cmd;
   cmd.Init(0, 0, kWidth, kHeight, GL_RGBA, GL_UNSIGNED_BYTE,
            pixels_shm_id, pixels_shm_offset,
-           result_shm_id, result_shm_offset);
+           result_shm_id, result_shm_offset,
+           false);
   EXPECT_EQ(error::kNoError, ExecuteCmd(cmd));
   for (GLint yy = 0; yy < kHeight; ++yy) {
     EXPECT_TRUE(emu.CompareRowSegment(
@@ -2477,34 +2480,41 @@ TEST_F(GLES2DecoderTest, ReadPixelsInvalidArgs) {
   ReadPixels cmd;
   cmd.Init(0, 0, -1, 1, GL_RGB, GL_UNSIGNED_BYTE,
            pixels_shm_id, pixels_shm_offset,
-           result_shm_id, result_shm_offset);
+           result_shm_id, result_shm_offset,
+           false);
   EXPECT_EQ(error::kNoError, ExecuteCmd(cmd));
   EXPECT_EQ(GL_INVALID_VALUE, GetGLError());
   cmd.Init(0, 0, 1, -1, GL_RGB, GL_UNSIGNED_BYTE,
            pixels_shm_id, pixels_shm_offset,
-           result_shm_id, result_shm_offset);
+           result_shm_id, result_shm_offset,
+           false);
   EXPECT_EQ(error::kNoError, ExecuteCmd(cmd));
   EXPECT_EQ(GL_INVALID_VALUE, GetGLError());
   cmd.Init(0, 0, 1, 1, GL_RGB, GL_INT,
            pixels_shm_id, pixels_shm_offset,
-           result_shm_id, result_shm_offset);
+           result_shm_id, result_shm_offset,
+           false);
   EXPECT_EQ(error::kNoError, ExecuteCmd(cmd));
   EXPECT_EQ(GL_INVALID_ENUM, GetGLError());
   cmd.Init(0, 0, 1, 1, GL_RGB, GL_UNSIGNED_BYTE,
            kInvalidSharedMemoryId, pixels_shm_offset,
-           result_shm_id, result_shm_offset);
+           result_shm_id, result_shm_offset,
+           false);
   EXPECT_NE(error::kNoError, ExecuteCmd(cmd));
   cmd.Init(0, 0, 1, 1, GL_RGB, GL_UNSIGNED_BYTE,
            pixels_shm_id, kInvalidSharedMemoryOffset,
-           result_shm_id, result_shm_offset);
+           result_shm_id, result_shm_offset,
+           false);
   EXPECT_NE(error::kNoError, ExecuteCmd(cmd));
   cmd.Init(0, 0, 1, 1, GL_RGB, GL_UNSIGNED_BYTE,
            pixels_shm_id, pixels_shm_offset,
-           kInvalidSharedMemoryId, result_shm_offset);
+           kInvalidSharedMemoryId, result_shm_offset,
+           false);
   EXPECT_NE(error::kNoError, ExecuteCmd(cmd));
   cmd.Init(0, 0, 1, 1, GL_RGB, GL_UNSIGNED_BYTE,
            pixels_shm_id, pixels_shm_offset,
-           result_shm_id, kInvalidSharedMemoryOffset);
+           result_shm_id, kInvalidSharedMemoryOffset,
+           false);
   EXPECT_NE(error::kNoError, ExecuteCmd(cmd));
 }
 
@@ -4932,7 +4942,8 @@ TEST_F(GLES2DecoderTest, ReadPixelsGLError) {
   ReadPixels cmd;
   cmd.Init(x, y, width, height, kFormat, GL_UNSIGNED_BYTE,
            pixels_shm_id, pixels_shm_offset,
-           result_shm_id, result_shm_offset);
+           result_shm_id, result_shm_offset,
+           false);
   EXPECT_EQ(error::kNoError, ExecuteCmd(cmd));
   EXPECT_EQ(GL_OUT_OF_MEMORY, GetGLError());
 }
@@ -6664,8 +6675,9 @@ TEST_F(GLES2DecoderWithShaderTest, UnClearedAttachmentsGetClearedOnReadPixels) {
   uint32 pixels_shm_offset = kSharedMemoryOffset + sizeof(*result);
   ReadPixels cmd;
   cmd.Init(0, 0, 1, 1, GL_RGBA, GL_UNSIGNED_BYTE,
-         pixels_shm_id, pixels_shm_offset,
-         result_shm_id, result_shm_offset);
+           pixels_shm_id, pixels_shm_offset,
+           result_shm_id, result_shm_offset,
+           false);
   EXPECT_EQ(error::kNoError, ExecuteCmd(cmd));
   EXPECT_EQ(GL_NO_ERROR, GetGLError());
 }
@@ -6724,8 +6736,9 @@ TEST_F(GLES2DecoderManualInitTest,
   uint32 pixels_shm_offset = kSharedMemoryOffset + sizeof(Result);
   ReadPixels cmd;
   cmd.Init(0, 0, 1, 1, GL_RGBA, GL_UNSIGNED_BYTE,
-         pixels_shm_id, pixels_shm_offset,
-         result_shm_id, result_shm_offset);
+           pixels_shm_id, pixels_shm_offset,
+           result_shm_id, result_shm_offset,
+           false);
   EXPECT_EQ(error::kNoError, ExecuteCmd(cmd));
   EXPECT_EQ(GL_NO_ERROR, GetGLError());
 }
diff --git a/gpu/command_buffer/service/gles2_cmd_validation_implementation_autogen.h b/gpu/command_buffer/service/gles2_cmd_validation_implementation_autogen.h
index ebe7e07..db9725d 100644
--- a/gpu/command_buffer/service/gles2_cmd_validation_implementation_autogen.h
+++ b/gpu/command_buffer/service/gles2_cmd_validation_implementation_autogen.h
@@ -300,6 +300,7 @@ static GLenum valid_query_target_table[] = {
   GL_COMMANDS_ISSUED_CHROMIUM,
   GL_LATENCY_QUERY_CHROMIUM,
   GL_ASYNC_PIXEL_TRANSFERS_COMPLETED_CHROMIUM,
+  GL_ASYNC_READ_PIXELS_COMPLETED_CHROMIUM,
 };
 
 static GLenum valid_read_pixel_format_table[] = {
diff --git a/gpu/command_buffer/service/query_manager.cc b/gpu/command_buffer/service/query_manager.cc
index e66478a..6d2f84a 100644
--- a/gpu/command_buffer/service/query_manager.cc
+++ b/gpu/command_buffer/service/query_manager.cc
@@ -223,9 +223,8 @@ bool AsyncPixelTransfersCompletedQuery::End(uint32 submit_count) {
   // on the current thread.
   manager()->decoder()->GetAsyncPixelTransferManager()->AsyncNotifyCompletion(
       mem_params,
-      base::Bind(AsyncPixelTransfersCompletedQuery::MarkAsCompletedThreadSafe,
+      base::Bind(&AsyncPixelTransfersCompletedQuery::MarkAsCompletedThreadSafe,
                  submit_count));
-
   return AddToPendingTransferQueue(submit_count);
 }
 
@@ -254,6 +253,58 @@ void AsyncPixelTransfersCompletedQuery::Destroy(bool /* have_context */) {
 AsyncPixelTransfersCompletedQuery::~AsyncPixelTransfersCompletedQuery() {
 }
 
+class AsyncReadPixelsCompletedQuery
+    : public QueryManager::Query,
+      public base::SupportsWeakPtr<AsyncReadPixelsCompletedQuery> {
+ public:
+  AsyncReadPixelsCompletedQuery(
+      QueryManager* manager, GLenum target, int32 shm_id, uint32 shm_offset);
+
+  virtual bool Begin() OVERRIDE;
+  virtual bool End(uint32 submit_count) OVERRIDE;
+  virtual bool Process() OVERRIDE;
+  virtual void Destroy(bool have_context) OVERRIDE;
+
+ protected:
+  void Complete();
+  virtual ~AsyncReadPixelsCompletedQuery();
+};
+
+AsyncReadPixelsCompletedQuery::AsyncReadPixelsCompletedQuery(
+    QueryManager* manager, GLenum target, int32 shm_id, uint32 shm_offset)
+    : Query(manager, target, shm_id, shm_offset) {
+}
+
+bool AsyncReadPixelsCompletedQuery::Begin() {
+  return true;
+}
+
+bool AsyncReadPixelsCompletedQuery::End(uint32 submit_count) {
+  manager()->decoder()->WaitForReadPixels(
+      base::Bind(&AsyncReadPixelsCompletedQuery::Complete,
+                 AsWeakPtr()));
+
+  return AddToPendingTransferQueue(submit_count);
+}
+
+void AsyncReadPixelsCompletedQuery::Complete() {
+  MarkAsCompleted(1);
+}
+
+bool AsyncReadPixelsCompletedQuery::Process() {
+  return !pending();
+}
+
+void AsyncReadPixelsCompletedQuery::Destroy(bool /* have_context */) {
+  if (!IsDeleted()) {
+    MarkAsDeleted();
+  }
+}
+
+AsyncReadPixelsCompletedQuery::~AsyncReadPixelsCompletedQuery() {
+}
+
+
 class GetErrorQuery : public QueryManager::Query {
  public:
   GetErrorQuery(
@@ -345,6 +396,10 @@ QueryManager::Query* QueryManager::CreateQuery(
       query = new AsyncPixelTransfersCompletedQuery(
           this, target, shm_id, shm_offset);
       break;
+    case GL_ASYNC_READ_PIXELS_COMPLETED_CHROMIUM:
+      query = new AsyncReadPixelsCompletedQuery(
+          this, target, shm_id, shm_offset);
+      break;
     case GL_GET_ERROR_QUERY_CHROMIUM:
       query = new GetErrorQuery(this, target, shm_id, shm_offset);
       break;
diff --git a/gpu/config/gpu_driver_bug_list_json.cc b/gpu/config/gpu_driver_bug_list_json.cc
index 1b02bf6..2ecfb07 100644
--- a/gpu/config/gpu_driver_bug_list_json.cc
+++ b/gpu/config/gpu_driver_bug_list_json.cc
@@ -385,6 +385,23 @@ const char kGpuDriverBugListJson[] = LONG_STRING_CONST(
       "features": [
         "use_non_zero_size_for_client_side_stream_buffers"
       ]
+    },
+    {
+      "id": 25,
+      "cr_bugs": [152225],
+      "description":
+          "Intel OSX drivers prior to mountain lion crashes when using PBOs",
+      "os": {
+        "type": "macosx",
+        "version": {
+          "op": "<",
+          "number": "10.8"
+        }
+      },
+      "vendor_id": "0x8086",
+      "features": [
+        "disable_async_readpixels"
+      ]
     }
   ]
 }
@@ -392,4 +409,3 @@ const char kGpuDriverBugListJson[] = LONG_STRING_CONST(
 );  // LONG_STRING_CONST macro
 
 }  // namespace gpu
-
diff --git a/gpu/config/gpu_driver_bug_workaround_type.h b/gpu/config/gpu_driver_bug_workaround_type.h
index 328fca0..41ccf2e 100644
--- a/gpu/config/gpu_driver_bug_workaround_type.h
+++ b/gpu/config/gpu_driver_bug_workaround_type.h
@@ -58,6 +58,8 @@
          use_current_program_after_successful_link)          \
   GPU_OP(USE_NON_ZERO_SIZE_FOR_CLIENT_SIDE_STREAM_BUFFERS,   \
          use_non_zero_size_for_client_side_stream_buffers)   \
+  GPU_OP(DISABLE_ASYNC_READPIXELS,                           \
+         disable_async_readpixels)                           \
 
 namespace gpu {
 
@@ -75,4 +77,3 @@ GPU_EXPORT std::string GpuDriverBugWorkaroundTypeToString(
 }  // namespace gpu
 
 #endif  // GPU_CONFIG_GPU_DRIVER_BUG_WORKAROUND_TYPE_H_
-