Bug 1847584 - Consistently throttle visibility:hidden frames. r=smaug

Before this patch OOP frames were being throttled but in-process ones
weren't.

Depends on D185643

Differential Revision: https://phabricator.services.mozilla.com/D185794

dom/base/Document.cpp

@@ -7084,6 +7084,12 @@ bool Document::ShouldThrottleFrameRequests() const {
     return true;
   }
 
+  if (mPresShell->IsUnderHiddenEmbedderElement()) {
+    // For display: none and visibility: hidden we always throttle, for
+    // consistency with OOP iframes.
+    return true;
+  }
+
   Element* el = GetEmbedderElement();
   if (!el) {
     // If we're not in-process, our refresh driver is throttled separately (via
@@ -7101,7 +7107,7 @@ bool Document::ShouldThrottleFrameRequests() const {
   // acceptable / unlikely to be human-perceivable, though we could improve on
   // it if needed by adding an intersection margin or something of that sort.
   const IntersectionInput input = DOMIntersectionObserver::ComputeInput(
-      *el->OwnerDoc(), /* aRoot = */ nullptr, /* aMargin = */ nullptr);
+      *el->OwnerDoc(), /* aRoot = */ nullptr, /* aRootMargin = */ nullptr);
   const IntersectionOutput output =
       DOMIntersectionObserver::Intersect(input, *el);
   return !output.Intersects();

dom/base/test/test_bug1639328.html

@@ -23,6 +23,9 @@
 <iframe id="display-none-http" style="display: none" src="https://example.com/tests/dom/base/test/file_bug1639328.html"></iframe>
 <iframe id="display-none-https" style="display: none" src="https://example.com/tests/dom/base/test/file_bug1639328.html"></iframe>
 <iframe id="display-none-same-origin" style="display: none" src="file_bug1639328.html"></iframe>
+<iframe id="vis-hidden-http" style="visibility: hidden" src="https://example.com/tests/dom/base/test/file_bug1639328.html"></iframe>
+<iframe id="vis-hidden-https" style="visibility: hidden" src="https://example.com/tests/dom/base/test/file_bug1639328.html"></iframe>
+<iframe id="vis-hidden-same-origin" style="visibility: hidden" src="file_bug1639328.html"></iframe>
 <script>
 SimpleTest.waitForExplicitFinish();
 
@@ -55,19 +58,30 @@ async function checkFrame(frame, shouldThrottle) {
   is(message.throttledFrameRequests, shouldThrottle, frame.id);
 }
 
+function shouldThrottle(frame) {
+  return frame.style.display == "none" || frame.style.visibility == "hidden";
+}
+
 onload = async function() {
   await SimpleTest.promiseFocus(window);
   await ticks(2);
   is(SpecialPowers.DOMWindowUtils.effectivelyThrottlesFrameRequests, false, "Should not be throttling main page");
   for (let frame of document.querySelectorAll("iframe")) {
-    let shouldThrottle = frame.style.display == "none";
-    await checkFrame(frame, shouldThrottle);
-    info("Switching display of " + frame.id);
-    frame.style.display = shouldThrottle ? "" : "none";
-    await checkFrame(frame, !shouldThrottle);
-    info("And switching display back for " + frame.id);
-    frame.style.display = shouldThrottle ? "none" : "";
-    await checkFrame(frame, shouldThrottle);
+    let originalShouldThrottle = shouldThrottle(frame);
+    await checkFrame(frame, originalShouldThrottle);
+    for (let prop of ["display", "visibility"]) {
+      info(`Switching ${prop} of ${frame.id}`);
+      let orig = frame.style[prop];
+      let throttledValue = prop == "display" ? "none" : "hidden";
+      frame.style[prop] = orig == throttledValue ? "" : throttledValue;
+      if (orig != throttledValue) {
+        is(shouldThrottle(frame), true, `Should throttle for ${prop}: ${throttledValue}`);
+      }
+      await checkFrame(frame, shouldThrottle(frame));
+      info(`Switching ${prop} back for ${frame.id}`);
+      frame.style[prop] = orig;
+      await checkFrame(frame, originalShouldThrottle);
+    }
   }
 
   SimpleTest.finish();

dom/base/test/test_bug1730284.html

@@ -36,7 +36,7 @@
 </style>
 <iframe class="visible"></iframe>
 <iframe class="display-none" data-throttled-expected></iframe>
-<iframe class="vis-hidden"></iframe>
+<iframe class="vis-hidden" data-throttled-expected></iframe>
 <iframe class="transparent"></iframe>
 <iframe class="zero-size"></iframe>
 <div class="scroller">