[Blink-Scheduler] Distinguish between normal and foreground-only renderers for monitoring load.

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index 93f9199020feb21dd6e960fadad12831fb720535..e554debf3d66498a25b778f72cb66a4ae3ab073a 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -59008,7 +59008,23 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="RendererScheduler.ForegroundOnlyRendererMainThreadLoad"
+    units="%">
+  <owner>karandeepb@chromium.org</owner>
+  <summary>
+    Renderer main thread load i.e. percentage of time spent on running tasks,
+    for renderers which are always foregrounded, e.g. extension renderers.
+
+    This metric is emitted when the renderer main thread task is completed, at
+    most once per minute per renderer amortized.
+  </summary>
+</histogram>
+
 <histogram name="RendererScheduler.ForegroundRendererMainThreadLoad" units="%">
+  <obsolete>
+    Deprecated 05/2017. Replaced with
+    RendererScheduler.ForegroundRendererMainThreadLoad2.
+  </obsolete>
   <owner>altimin@chromium.org</owner>
   <summary>
     Renderer main thread load when renderer is foregrounded, i.e. percentage of
@@ -59020,6 +59036,19 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="RendererScheduler.ForegroundRendererMainThreadLoad2" units="%">
+  <owner>altimin@chromium.org</owner>
+  <summary>
+    Renderer main thread load when renderer is foregrounded, i.e. percentage of
+    time spent on running tasks. This excludes renderers which are always
+    foregrounded, e.g. extension renderers.
+
+    This metric is emitted when the renderer main thread task is completed or
+    renderer is backgrounded or foregrounded, at most once per minute per
+    renderer amortized.
+  </summary>
+</histogram>
+
 <histogram name="RendererScheduler.NumberOfTasksPerQueueType"
     enum="RendererSchedulerTaskQueueType">
   <owner>altimin@chromium.org,alexclarke@chromium.org</owner>