Throttle rendering pipeline for invisible frames

third_party/WebKit/Source/core/dom/Document.cpp

Index: third_party/WebKit/Source/core/dom/Document.cpp
diff --git a/third_party/WebKit/Source/core/dom/Document.cpp b/third_party/WebKit/Source/core/dom/Document.cpp
index a6bc05b6a25ebf04bf9d4d3ceab14e74b4840986..a90eed34006871a32ea09f6b1d5115803a90a566 100644
--- a/third_party/WebKit/Source/core/dom/Document.cpp
+++ b/third_party/WebKit/Source/core/dom/Document.cpp
@@ -1531,7 +1531,8 @@ void Document::scheduleLayoutTreeUpdate()
     ASSERT(shouldScheduleLayoutTreeUpdate());
     ASSERT(needsLayoutTreeUpdate());
 
-    page()->animator().scheduleVisualUpdate();
+    if (!view() || !view()->shouldThrottleRendering())

[esprehn, 2015/10/14 22:09:46]

we shouldn't be able to get here without a view(), it would hit one of the
asserts above because the document wouldn't be isActive(). no need to null check
view()

[Sami, 2015/10/16 16:48:08]

Thanks, I didn't realize isActive() implies view().

+        page()->animator().scheduleVisualUpdate();
     m_lifecycle.ensureStateAtMost(DocumentLifecycle::VisualUpdatePending);
 
     TRACE_EVENT_INSTANT1(TRACE_DISABLED_BY_DEFAULT("devtools.timeline"), "ScheduleStyleRecalculation", TRACE_EVENT_SCOPE_THREAD, "data", InspectorRecalculateStylesEvent::data(frame()));
@@ -1721,6 +1722,9 @@ void Document::updateLayoutTree(StyleRecalcChange change)
     if (!view() || !isActive())
         return;
 
+    if (view()->shouldThrottleRenderingIfAllowed())
+        return;
+
     if (change != Force && !needsLayoutTreeUpdate()) {
         ASSERT(lifecycle().state() != DocumentLifecycle::VisualUpdatePending);
         return;
@@ -1788,6 +1792,9 @@ void Document::updateLayoutTree(StyleRecalcChange change)
 
 void Document::updateStyle(StyleRecalcChange change)
 {
+    if (view() && view()->shouldThrottleRenderingIfAllowed())

[esprehn, 2015/10/14 22:09:46]

you must have a view here, no need to null check, you can add an
ASSERT(isActive()) if you want

[Sami, 2015/10/16 16:48:08]

Done.

+        return;
+
     TRACE_EVENT_BEGIN0("blink,blink_style", "Document::updateStyle");
     unsigned initialResolverAccessCount = styleEngine().resolverAccessCount();
 
@@ -1905,16 +1912,18 @@ void Document::updateLayout()
     if (HTMLFrameOwnerElement* owner = ownerElement())
         owner->document().updateLayout();
 
+    lifecycle().setThrottlingMode(DocumentLifecycle::ThrottlingMode::Disallow);

[esprehn, 2015/10/14 22:09:45]

Lets add a scope object for this instead of manual setting/unsetting.

DocumentLifecycle::ThrottleScope

[Sami, 2015/10/16 16:48:08]

Much cleaner, done. In case it isn't obvious, I made the scope signify that
throttling is *not* allowed because that is generally what call sites want to do
(e.g., doing a synchronous style recalc inside a context that otherwise allows
throttling).

     updateLayoutTreeIfNeeded();
 
-    if (!isActive())
-        return;
+    if (isActive()) {
+        if (frameView->needsLayout())
+            frameView->layout();
 
-    if (frameView->needsLayout())
-        frameView->layout();
+        if (lifecycle().state() < DocumentLifecycle::LayoutClean)
+            lifecycle().advanceTo(DocumentLifecycle::LayoutClean);
+    }
 
-    if (lifecycle().state() < DocumentLifecycle::LayoutClean)
-        lifecycle().advanceTo(DocumentLifecycle::LayoutClean);
+    lifecycle().setThrottlingMode(DocumentLifecycle::ThrottlingMode::Allow);
 }
 
 void Document::layoutUpdated()