In CanvasContext::doFrame, make a separate call to computeFrameTimeNanos

and save the result. Then pass that value to
UiFrameInfoBuilder::setVsync as both arguments.

The order of function argument evaluation is undefined in C++. Because
the value returned from TimeLord::latestVsync may be changed by
the preceding call to TimeLord::computeFrameTimeNanos the values of the
arguments passed to UiFrameInfoBuilder::setVsync is also undefined. This
change removes any ambiguity.

Change-Id: Ie71ee453f9ccc725edfe5f7cc9b277f2a809dfdc

libs/hwui/renderthread/CanvasContext.cpp

@@ -289,11 +289,11 @@ void CanvasContext::doFrame() {
 
     ATRACE_CALL();
 
+    nsecs_t vsync = mRenderThread.timeLord().computeFrameTimeNanos();
     int64_t frameInfo[UI_THREAD_FRAME_INFO_SIZE];
     UiFrameInfoBuilder(frameInfo)
         .addFlag(FrameInfoFlags::RTAnimation)
-        .setVsync(mRenderThread.timeLord().computeFrameTimeNanos(),
-                mRenderThread.timeLord().latestVsync());
+        .setVsync(vsync, vsync);
 
     TreeInfo info(TreeInfo::MODE_RT_ONLY, mRenderThread.renderState());
     prepareTree(info, frameInfo, systemTime(CLOCK_MONOTONIC));