DevTools: fix animations panel after image loading became async

third_party/WebKit/Source/devtools/front_end/animation/AnimationTimeline.js

Index: third_party/WebKit/Source/devtools/front_end/animation/AnimationTimeline.js
diff --git a/third_party/WebKit/Source/devtools/front_end/animation/AnimationTimeline.js b/third_party/WebKit/Source/devtools/front_end/animation/AnimationTimeline.js
index e6ecf4a074d27b93c4b27d29de9ec95a478e5d92..9818a93a51f71bf185cfd0fcd193dd73b2ec004a 100644
--- a/third_party/WebKit/Source/devtools/front_end/animation/AnimationTimeline.js
+++ b/third_party/WebKit/Source/devtools/front_end/animation/AnimationTimeline.js
@@ -191,12 +191,23 @@ WebInspector.AnimationTimeline.prototype = {
                 animGroup = group;
         }
         console.assert(animGroup);
-        var screenshots = animGroup.screenshots();
+        var screenshots = animGroup.screenshots(onImageLoad);
         if (!screenshots.length)
             return;
-        var content = new WebInspector.AnimationScreenshotPopover(screenshots);
-        popover.setNoMargins(true);
-        popover.showView(content, anchor);
+        if (screenshots[0].complete)

[lushnikov, 2016/08/01 23:16:11]

why do we care only about the 0's screenshot?

[luoe, 2016/08/02 00:24:10]

We shouldn't :)
Changed to keep a counter for remaining loading images.  When it hits 0, we call
onImageLoad().

+            onImageLoad();
+
+        var loaded = false;
+        function onImageLoad()
+        {
+            if (loaded)
+                return;
+            loaded = true;
+
+            var content = new WebInspector.AnimationScreenshotPopover(screenshots);
+            popover.setNoMargins(true);
+            popover.showView(content, anchor);
+        }
     },
 
     _onHidePopover: function()