Animations: Allow document animation timelines to have a playback rate

Source/core/inspector/InspectorPageAgent.cpp

Index: Source/core/inspector/InspectorPageAgent.cpp
diff --git a/Source/core/inspector/InspectorPageAgent.cpp b/Source/core/inspector/InspectorPageAgent.cpp
index d218e8ba0629fef86666b44d659f2a4cdd9785b2..48e964f56ca5aa764ac55245851022124eeec1c8 100644
--- a/Source/core/inspector/InspectorPageAgent.cpp
+++ b/Source/core/inspector/InspectorPageAgent.cpp
@@ -36,6 +36,7 @@
 #include "bindings/core/v8/ScriptRegexp.h"
 #include "core/HTMLNames.h"
 #include "core/UserAgentStyleSheets.h"
+#include "core/animation/AnimationTimeline.h"
 #include "core/css/StyleSheetContents.h"
 #include "core/css/resolver/StyleResolver.h"
 #include "core/css/resolver/ViewportStyleResolver.h"
@@ -1475,6 +1476,14 @@ void InspectorPageAgent::setShowViewportSizeOnResize(ErrorString*, bool show, co
     m_state->setBoolean(PageAgentState::showGridOnResize, asBool(showGrid));
 }
 
+void InspectorPageAgent::setAnimationsPlaybackRate(ErrorString*, double playbackRate)
+{
+    for (Frame* frame = m_page->mainFrame(); frame; frame = frame->tree().traverseNext()) {
+        if (frame->isLocalFrame())
+            toLocalFrame(frame)->document()->timeline().setPlaybackRate(playbackRate);
+    }
+}
+
 void InspectorPageAgent::clearEditedResourcesContent()
 {
     m_editedResourceContent.clear();