Re-land: gpu: Add CHROMIUM_sync_query extension.

gpu/command_buffer/service/query_manager.cc

Index: gpu/command_buffer/service/query_manager.cc
diff --git a/gpu/command_buffer/service/query_manager.cc b/gpu/command_buffer/service/query_manager.cc
index 9f1d3a7169c31b5c1ee640b07f6c08a71623b18b..a9a4c0e5a6eac9ad2380e820bb2feaf0c782aa58 100644
--- a/gpu/command_buffer/service/query_manager.cc
+++ b/gpu/command_buffer/service/query_manager.cc
@@ -16,6 +16,7 @@
 #include "gpu/command_buffer/service/error_state.h"
 #include "gpu/command_buffer/service/feature_info.h"
 #include "gpu/command_buffer/service/gles2_cmd_decoder.h"
+#include "ui/gl/gl_fence.h"
 
 namespace gpu {
 namespace gles2 {
@@ -389,6 +390,57 @@ void GetErrorQuery::Destroy(bool /* have_context */) {
 GetErrorQuery::~GetErrorQuery() {
 }
 
+class CommandsCompletedQuery : public QueryManager::Query {
+ public:
+  CommandsCompletedQuery(QueryManager* manager,
+                         GLenum target,
+                         int32 shm_id,
+                         uint32 shm_offset);
+
+  // Overridden from QueryManager::Query:
+  virtual bool Begin() OVERRIDE;
+  virtual bool End(base::subtle::Atomic32 submit_count) OVERRIDE;
+  virtual bool Process() OVERRIDE;
+  virtual void Destroy(bool have_context) OVERRIDE;
+
+ protected:
+  virtual ~CommandsCompletedQuery();
+
+ private:
+  scoped_ptr<gfx::GLFence> fence_;
+};
+
+CommandsCompletedQuery::CommandsCompletedQuery(QueryManager* manager,
+                                               GLenum target,
+                                               int32 shm_id,
+                                               uint32 shm_offset)
+    : Query(manager, target, shm_id, shm_offset) {}
+
+bool CommandsCompletedQuery::Begin() {
+  return true;
+}
+
+bool CommandsCompletedQuery::End(base::subtle::Atomic32 submit_count) {
+  fence_.reset(gfx::GLFence::CreateWithoutFlush());

[no sievers, 2014/04/15 23:53:37]

Make sure piman@ is ok with this being used here :)

Also, can we maybe find a place where we can imply a flush?
Maybe at least from the client when the result is queried?

[piman, 2014/04/16 00:32:03]

The client only forces a shallow flush, because the (service-side)
glGetQueryObjectuivEXT is expected to imply a glFlush.

Note the wording in
http://www.khronos.org/registry/gles/extensions/EXT/EXT_occlusion_query_boole...:
    Querying the state for any given query object forces that occlusion query 
    to complete within a finite amount of time. Repeatedly querying the 
    QUERY_RESULT_AVAILABLE_EXT state for any given query object is guaranteed
    to return true eventually.


I'd prefer we explicitly flush here (GLFence::Create), unless we can actually
measure performance issues. If so, we can relax flushing here, but then we need
to implement the above guarantee somehow (and add tests for it).

[reveman, 2014/04/16 01:28:47]

Ah, looked like QueryTracker::Query::CheckResultsAvailable was issuing a real
flush but I see now that it doesn't. CommandBufferHelper and GLES2CmdHelper both
implementing a function named Flush and GLES2CmdHelper inheriting from
CommandBufferHelper is a bit confusing..
I changed this to gfx::GLFence::Create() in latest patch. Not sure what the
performance impact of a flush after each CopyTexture and before each SwapBuffers
will have but I can look at that as a follow up.

+  DCHECK(fence_);

[piman, 2014/04/16 00:32:03]

gfx::GLFence::Create (with or without flush) will fail if the underlying
extension is not available. See comment in build_gles2_cmd_buffer.py
That's why we need to refuse the enum.

[reveman, 2014/04/16 01:28:47]

Got it.

+  return AddToPendingQueue(submit_count);
+}
+
+bool CommandsCompletedQuery::Process() {
+  if (fence_ && !fence_->HasCompleted())
+    return true;
+  return MarkAsCompleted(0);
+}
+
+void CommandsCompletedQuery::Destroy(bool have_context) {
+  if (have_context && !IsDeleted()) {
+    fence_.reset();
+    MarkAsDeleted();
+  }
+}
+
+CommandsCompletedQuery::~CommandsCompletedQuery() {}
+
 QueryManager::QueryManager(
     GLES2Decoder* decoder,
     FeatureInfo* feature_info)
@@ -444,6 +496,9 @@ QueryManager::Query* QueryManager::CreateQuery(
     case GL_GET_ERROR_QUERY_CHROMIUM:
       query = new GetErrorQuery(this, target, shm_id, shm_offset);
       break;
+    case GL_COMMANDS_COMPLETED_CHROMIUM:
+      query = new CommandsCompletedQuery(this, target, shm_id, shm_offset);
+      break;
     default: {
       GLuint service_id = 0;
       glGenQueriesARB(1, &service_id);