Instrumenting internals of BrowserGpuChannelHostFactory::EstablishRequest::FinishOnMain to locate jankiness.

BrowserGpuChannelHostFactory::EstablishRequest::FinishOnMain is responsible
for 17.9 janks per hour in UI thread. I need to instrument
the code inside it to find out which part causes jank.

Dear reviewer! If you know where the jank is, or have ideas where I need to add
more instrumentations, please let me know!

This is a mechanical change that adds instrumentation required to locate the
source of jankiness (i.e. a long-running fragment of code executed as a part of
the task that causes jank) in the code. See the bug for details on what kind of
jank we are after.
A number of similar CLs were landed, and none of them caused issues. They've
helped to find and fix janky code. The code of the instrumentation is highly
optimized and is not expected to affect performance. The code simply creates a
diagnostic task which is identical to ones created by PostTask or IPC message
handlers. The task gets created only in developer build and in Canary channel.

BUG=430106

Review URL: https://codereview.chromium.org/691143003

Cr-Commit-Position: refs/heads/master@{#302810}

1 files changed, 13 insertions, 0 deletions

diff --git a/content/common/gpu/client/webgraphicscontext3d_command_buffer_impl.cc b/content/common/gpu/client/webgraphicscontext3d_command_buffer_impl.cc
index bc76245c..a5ba180 100644
--- a/content/common/gpu/client/webgraphicscontext3d_command_buffer_impl.cc
+++ b/content/common/gpu/client/webgraphicscontext3d_command_buffer_impl.cc
@@ -22,6 +22,7 @@
 #include "base/message_loop/message_loop.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram.h"
+#include "base/tracked_objects.h"
 #include "content/common/gpu/client/gpu_channel_host.h"
 #include "content/public/common/content_constants.h"
 #include "content/public/common/content_switches.h"
@@ -127,8 +128,18 @@ bool WebGraphicsContext3DCommandBufferImpl::MaybeInitializeGL() {
 
   TRACE_EVENT0("gpu", "WebGfxCtx3DCmdBfrImpl::MaybeInitializeGL");
 
+  // Below, we perform an expensive one-time initialization that is required to
+  // get first pixels to the screen. This can't be called "jank" since there is
+  // nothing on the screen. Using TaskStopwatch to exclude the operation from
+  // jank calculations.
+  tracked_objects::TaskStopwatch stopwatch;
+  stopwatch.Start();
+
   if (!CreateContext(surface_id_ != 0)) {
     Destroy();
+
+    stopwatch.Stop();
+
     initialize_failed_ = true;
     return false;
   }
@@ -146,6 +157,8 @@ bool WebGraphicsContext3DCommandBufferImpl::MaybeInitializeGL() {
 
   real_gl_->SetErrorMessageCallback(getErrorMessageCallback());
 
+  stopwatch.Stop();
+
   visible_ = true;
   initialized_ = true;
   return true;