Add logging of statistics of Fabric commits

Summary:
This diff adds extra logging to track how long does it take to exeucte different stages of the fabric commit

changelog: [internal] internal

Reviewed By: philIip

Differential Revision: D33183070

fbshipit-source-id: 69e31bef69c9d9ec57dc7e00e4c36e278eb30cb6

ReactAndroid/src/main/java/com/facebook/react/fabric/FabricUIManager.java

@@ -716,6 +716,7 @@ public class FabricUIManager implements UIManager, LifecycleEventListener {
     // When Binding.cpp calls scheduleMountItems during a commit phase, it always calls with
     // a BatchMountItem. No other sites call into this with a BatchMountItem, and Binding.cpp only
     // calls scheduleMountItems with a BatchMountItem.
+    long scheduleMountItemStartTime = SystemClock.uptimeMillis();
     boolean isBatchMountItem = mountItem instanceof IntBufferBatchMountItem;
     boolean shouldSchedule =
         (isBatchMountItem && ((IntBufferBatchMountItem) mountItem).shouldSchedule())
@@ -731,7 +732,7 @@ public class FabricUIManager implements UIManager, LifecycleEventListener {
       mCommitStartTime = commitStartTime;
       mLayoutTime = layoutEndTime - layoutStartTime;
       mFinishTransactionCPPTime = finishTransactionEndTime - finishTransactionStartTime;
-      mFinishTransactionTime = SystemClock.uptimeMillis() - finishTransactionStartTime;
+      mFinishTransactionTime = scheduleMountItemStartTime - finishTransactionStartTime;
       mDispatchViewUpdatesTime = SystemClock.uptimeMillis();
     }
 
@@ -766,6 +767,23 @@ public class FabricUIManager implements UIManager, LifecycleEventListener {
       ReactMarker.logFabricMarker(
           ReactMarkerConstants.FABRIC_LAYOUT_END, null, commitNumber, layoutEndTime);
       ReactMarker.logFabricMarker(ReactMarkerConstants.FABRIC_COMMIT_END, null, commitNumber);
+
+      if (ENABLE_FABRIC_LOGS) {
+        FLog.e(
+            TAG,
+            "Statistic of Fabric commit #: "
+                + commitNumber
+                + "\n - Total commit time: "
+                + (finishTransactionEndTime - commitStartTime)
+                + " ms.\n - Layout: "
+                + mLayoutTime
+                + " ms.\n - Diffing: "
+                + (diffEndTime - diffStartTime)
+                + " ms.\n"
+                + " - FinishTransaction (Diffing + Processing + Serialization of MountingInstructions): "
+                + mFinishTransactionCPPTime
+                + " ms.");
+      }
     }
   }