Add -ifsameorigin to autoplay experiment.

third_party/WebKit/Source/core/html/AutoplayExperimentHelper.cpp

Index: third_party/WebKit/Source/core/html/AutoplayExperimentHelper.cpp
diff --git a/third_party/WebKit/Source/core/html/AutoplayExperimentHelper.cpp b/third_party/WebKit/Source/core/html/AutoplayExperimentHelper.cpp
index 46e4df6327b5081d86421ee2b5b016e5e24639b7..895ffd1127df1eb21d28c09a03e3868783f702d0 100644
--- a/third_party/WebKit/Source/core/html/AutoplayExperimentHelper.cpp
+++ b/third_party/WebKit/Source/core/html/AutoplayExperimentHelper.cpp
@@ -295,6 +295,25 @@ bool AutoplayExperimentHelper::maybeStartPlaying()
     return true;
 }
 
+bool AutoplayExperimentHelper::isSameOrigin() const
+{
+    bool sameOrigin = true;
+    LocalFrame* frame = client().frame();
+    if (!frame)
+        return true;
+
+    const SecurityOrigin* origin = frame->securityContext()->getSecurityOrigin();

[ojan, 2016/04/26 01:13:57]

Can you move this into a helper function on Frame.h? That way it can be used
here and in FrameView::notifyRenderThrottlingObservers().

[liberato (no reviews please), 2016/04/26 18:30:24]

moved into a helper function.  however, i used mounir's UseCounter check rather
than one the one in notifyRender...(), so i didn't update the latter to use the
helper.  seemed pretty similar, but didn't want to make an unrelated change
that's not just refactoring.

+    for (Frame* parentFrame = frame->tree().parent(); parentFrame; parentFrame = parentFrame->tree().parent()) {
+        const SecurityOrigin* parentOrigin = parentFrame->securityContext()->getSecurityOrigin();
+        if (!origin->canAccess(parentOrigin)) {
+            sameOrigin = false;
+            break;
+        }
+    }

[mlamouri (slow - plz ping), 2016/04/26 14:41:40]

I think you only want to check top() here. This is how we usually consider
cross-origin iframes, see:
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...

[liberato (no reviews please), 2016/04/26 18:30:24]

done, and updated UseCounter::count...frame().

+
+    return sameOrigin;
+}
+
 bool AutoplayExperimentHelper::isEligible() const
 {
     if (m_mode == Mode::ExperimentOff)
@@ -326,6 +345,16 @@ bool AutoplayExperimentHelper::isEligible() const
         && !client().isLegacyViewportType())
         return false;
 
+    // If we require same-origin, then check the origin.  If we additionally
+    // require "or muted", then also allow autoplay in that case.
+    if (enabled(IfSameOrigin)) {
+        if (!isSameOrigin()) {
+            if (!enabled(OrMuted) || !client().muted()) {
+                return false;

[mlamouri (slow - plz ping), 2016/04/26 14:41:40]

Quite a bit of nesting, maybe you can merge `enabled(IfSameOrigin)` and
`!isSameOrigin()`

[liberato (no reviews please), 2016/04/26 18:30:24]

Done.

+            }
+        }
+    }
+
     // If we require muted media and this is muted, then it is eligible.
     if (enabled(IfMuted))
         return client().muted();
@@ -391,6 +420,10 @@ AutoplayExperimentHelper::Mode AutoplayExperimentHelper::fromString(const String
         value |= IfMuted;
     if (mode.contains("-ifmobile"))
         value |= IfMobile;
+    if (mode.contains("-ifsameorigin"))
+        value |= IfSameOrigin;
+    if (mode.contains("-ormuted"))
+        value |= OrMuted;
     if (mode.contains("-playmuted"))
         value |= PlayMuted;