When --disable-gpu-vsync, run requestAnimFrame callbacks at top speed.

content/renderer/render_widget.cc

Index: content/renderer/render_widget.cc
diff --git a/content/renderer/render_widget.cc b/content/renderer/render_widget.cc
index 98d6a4dd19488ec36b28747b2e5fb6bb12d118ad..af7533872611400db203e828940d07fd9be45ce8 100644
--- a/content/renderer/render_widget.cc
+++ b/content/renderer/render_widget.cc
@@ -30,6 +30,7 @@
 #include "ui/gfx/point.h"
 #include "ui/gfx/size.h"
 #include "ui/gfx/surface/transport_dib.h"
+#include "ui/gfx/gl/gl_switches.h"
 #include "webkit/glue/webkit_glue.h"
 #include "webkit/plugins/npapi/webplugin.h"
 #include "webkit/plugins/ppapi/ppapi_plugin_instance.h"
@@ -585,7 +586,7 @@ void RenderWidget::AnimationCallback() {
   animation_task_posted_ = false;
   if (!animation_update_pending_)
     return;
-  if (!animation_floor_time_.is_null()) {
+  if (!animation_floor_time_.is_null() && IsRenderingVSyncd()) {
     // Record when we fired (according to base::Time::Now()) relative to when
     // we posted the task to quantify how much the base::Time/base::TimeTicks
     // skew is affecting animations.
@@ -603,14 +604,19 @@ void RenderWidget::AnimationCallback() {
 void RenderWidget::AnimateIfNeeded() {
   if (!animation_update_pending_)
     return;
+
+  // Target 60FPS if vsync is on. Go as fast as we can if vsync is off.
+  int animationInterval = IsRenderingVSyncd() ? 16 : 0;
+
   base::Time now = base::Time::Now();
   if (now >= animation_floor_time_) {
-    animation_floor_time_ = now + base::TimeDelta::FromMilliseconds(16);
-    // Set a timer to call us back after 16ms (targetting 60FPS) before
+    animation_floor_time_ = now +
+        base::TimeDelta::FromMilliseconds(animationInterval);
+    // Set a timer to call us back after animationInterval before
     // running animation callbacks so that if a callback requests another
     // we'll be sure to run it at the proper time.
     MessageLoop::current()->PostDelayedTask(FROM_HERE, NewRunnableMethod(
-        this, &RenderWidget::AnimationCallback), 16);
+        this, &RenderWidget::AnimationCallback), animationInterval);
     animation_task_posted_ = true;
     animation_update_pending_ = false;
 #ifdef WEBWIDGET_HAS_ANIMATE_CHANGES
@@ -620,6 +626,7 @@ void RenderWidget::AnimateIfNeeded() {
 #endif
     return;
   }
+  TRACE_EVENT0("renderer", "EarlyOut_AnimatedTooRecently");
   if (animation_task_posted_)
     return;
   // This code uses base::Time::Now() to calculate the floor and next fire
@@ -636,6 +643,15 @@ void RenderWidget::AnimateIfNeeded() {
       NewRunnableMethod(this, &RenderWidget::AnimationCallback), delay);
 }
 
+bool RenderWidget::IsRenderingVSyncd() {
+  // TODO(nduca): Forcing a driver to disable vsync (e.g. in a control panel) is
+  // not caught by this check. This will lead to artificially low frame rates
+  // for people who force vsync off at a driver level and expect Chrome to speed
+  // up.
+  return !CommandLine::ForCurrentProcess()->HasSwitch(

[jamesr, 2011/06/02 22:07:53]

nitpick: this is doing a string comparison (and a conversion to lowercase on
windows) on every tick, which with vsync off will be pretty often.  this value
can never change for the lifetime of the process, so could you stash the results
in a static bool and just return that?  the command line strings can be pretty
long sometimes

+      switches::kDisableGpuVsync);
+}
+
 void RenderWidget::InvalidationCallback() {
   invalidation_task_posted_ = false;
   DoDeferredUpdateAndSendInputAck();