Add GPU.GPUChannelHostWaitTime.MicroSeconds histogram

GPU.GPUChannelHostWaitTime.MicroSeconds records the amount of time the
browser main thread spends blocked on sync IPCs to the GPU. This is
measuring the same value as GPU.GPUChannelHostWaitTime but with
different bucketing. GPU.GPUChannelHostWaitTime only cared about large
values and we do not wish the change the existing bucketing for it.

Bug: 1006924
Change-Id: I55447d3bd54cb7b24c84a6a4f5613880683cf571
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1816960
Commit-Queue: kylechar <kylechar@chromium.org>
Reviewed-by: Zhenyao Mo <zmo@chromium.org>
Reviewed-by: Maggie Chen <magchen@chromium.org>
Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#699973}

gpu/ipc/client/gpu_channel_host.cc

@@ -98,10 +98,18 @@ bool GpuChannelHost::Send(IPC::Message* msg) {
   bool signaled =
       pending_sync.done_event->TimedWait(kGpuChannelHostMaxWaitTime);
 
+  base::TimeDelta wait_duration = base::TimeTicks::Now() - start_time;
+
   // Histogram of wait-for-sync time, used for monitoring the GPU watchdog.
-  UMA_HISTOGRAM_CUSTOM_TIMES(
-      "GPU.GPUChannelHostWaitTime", base::TimeTicks::Now() - start_time,
-      base::TimeDelta::FromSeconds(1), kGpuChannelHostMaxWaitTime, 50);
+  UMA_HISTOGRAM_CUSTOM_TIMES("GPU.GPUChannelHostWaitTime", wait_duration,
+                             base::TimeDelta::FromSeconds(1),
+                             kGpuChannelHostMaxWaitTime, 50);
+
+  // Histogram to measure how long the browser UI thread spends blocked.
+  UMA_HISTOGRAM_CUSTOM_MICROSECONDS_TIMES(
+      "GPU.GPUChannelHostWaitTime.MicroSeconds", wait_duration,
+      base::TimeDelta::FromMicroseconds(10), base::TimeDelta::FromSeconds(10),
+      50);
 
   // Continue waiting for the event if not signaled
   if (!signaled)

tools/metrics/histograms/histograms.xml

@@ -50588,6 +50588,15 @@ uploading your change for review.
   </summary>
 </histogram>
 
+<histogram name="GPU.GPUChannelHostWaitTime.MicroSeconds" units="microseconds"
+    expires_after="M81">
+  <owner>kylechar@chromium.org</owner>
+  <summary>
+    Records how long the browser UI thread spent blocked for a sync IPC sent
+    using GpuChannelHost to see if it's contributing to jank.
+  </summary>
+</histogram>
+
 <histogram name="GPU.GpuGeneration" enum="GpuSeriesType" expires_after="M90">
   <owner>sunnyps@chromium.org</owner>
   <owner>zmo@chromium.org</owner>