Bug 1649313 - Add SkippedComposite markers. r=nical

Differential Revision: https://phabricator.services.mozilla.com/D82636

gfx/layers/wr/WebRenderBridgeParent.cpp

@@ -1963,6 +1963,11 @@ void WebRenderBridgeParent::CompositeToTarget(VsyncId aId,
   AUTO_PROFILER_TRACING_MARKER("Paint", "CompositeToTarget", GRAPHICS);
   if (mPaused || !mReceivedDisplayList) {
     ResetPreviousSampleTime();
+    TimeStamp now = TimeStamp::Now();
+    PROFILER_ADD_TEXT_MARKER("SkippedComposite",
+                             mPaused ? "Paused"_ns
+                                     : "No display list"_ns,
+                             JS::ProfilingCategoryPair::GRAPHICS, now, now);
     return;
   }
 
@@ -1980,6 +1985,11 @@ void WebRenderBridgeParent::CompositeToTarget(VsyncId aId,
         id.mSkippedComposites++;
       }
     }
+
+    TimeStamp now = TimeStamp::Now();
+    PROFILER_ADD_TEXT_MARKER("SkippedComposite",
+                             "Too many pending frames"_ns,
+                             JS::ProfilingCategoryPair::GRAPHICS, now, now);
     return;
   }
   MaybeGenerateFrame(aId, /* aForceGenerateFrame */ false);
@@ -2003,6 +2013,10 @@ void WebRenderBridgeParent::MaybeGenerateFrame(VsyncId aId,
     // Skip WR render during paused state.
     if (cbp->IsPaused()) {
       TimeStamp now = TimeStamp::Now();
+      PROFILER_ADD_TEXT_MARKER(
+          "SkippedComposite",
+          "CompositorBridgeParent is paused"_ns,
+          JS::ProfilingCategoryPair::GRAPHICS, now, now);
       cbp->NotifyPipelineRendered(mPipelineId, mWrEpoch, VsyncId(), now, now,
                                   now);
       return;
@@ -2037,6 +2051,9 @@ void WebRenderBridgeParent::MaybeGenerateFrame(VsyncId aId,
 
   if (!generateFrame) {
     // Could skip generating frame now.
+    PROFILER_ADD_TEXT_MARKER("SkippedComposite",
+                             "No reason to generate frame"_ns,
+                             JS::ProfilingCategoryPair::GRAPHICS, start, start);
     ResetPreviousSampleTime();
     return;
   }