Remove the fullscreen element stack exemption for webkitRequestFullScreen()

This exemption allowed the fullscreen element stack to get into a state
not otherwise possible, namely with elements in any order as opposed to
in tree order. It also seemed possible to enter fullscreen in a sibling
iframe, leading to a (cross-document) set of fullscreen elements forming
a tree instead of a simple chain, a case without any test coverage.

Removing the exemption means that a webkitfullscreenerror event will be
fired if one is already in fullscreen and requests fullscreen for an
element other than a descendant of the current fullscreen element.

The use counter was intended to tell whether any content depends on this
or not, but data will not be available for a long time yet. In order to
be affected one needs to, in fullscreen, have a currently visible button
request fullscreen for an element currently not visible, which seems
far-fetched, so site compat is probably not a problem.

The use counter for webkitRequestFullScreen() provides an upper bound:
http://www.chromestatus.com/metrics/feature/timeline/popularity/177

BUG=383813

Review URL: https://codereview.chromium.org/458223003

git-svn-id: svn://svn.chromium.org/blink/trunk@180243 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/LayoutTests/fullscreen/full-screen-css-expected.txt

@@ -2,14 +2,14 @@ EXPECTED (document.defaultView.getComputedStyle(span, null).getPropertyValue('ba
 EXPECTED (document.defaultView.getComputedStyle(document.documentElement, null).getPropertyValue('background-color') == 'rgba(0, 0, 0, 0)') OK
 EXPECTED (document.defaultView.getComputedStyle(document.documentElement, null).getPropertyValue('color') == 'rgb(0, 0, 0)') OK
 EVENT(webkitfullscreenchange)
-EXPECTED (document.webkitCurrentFullScreenElement == '[object HTMLSpanElement]') OK
-EXPECTED (document.defaultView.getComputedStyle(span, null).getPropertyValue('background-color') == 'rgb(0, 255, 0)') OK
-EXPECTED (document.defaultView.getComputedStyle(document.documentElement, null).getPropertyValue('background-color') == 'rgb(255, 0, 0)') OK
-EXPECTED (document.defaultView.getComputedStyle(document.documentElement, null).getPropertyValue('color') == 'rgb(0, 0, 255)') OK
-EVENT(webkitfullscreenchange)
 EXPECTED (document.webkitCurrentFullScreenElement == '[object HTMLHtmlElement]') OK
 EXPECTED (document.defaultView.getComputedStyle(span, null).getPropertyValue('background-color') == 'rgba(0, 0, 0, 0)') OK
 EXPECTED (document.defaultView.getComputedStyle(document.documentElement, null).getPropertyValue('background-color') == 'rgb(0, 255, 0)') OK
 EXPECTED (document.defaultView.getComputedStyle(document.documentElement, null).getPropertyValue('color') == 'rgb(0, 0, 255)') OK
+EVENT(webkitfullscreenchange)
+EXPECTED (document.webkitCurrentFullScreenElement == '[object HTMLSpanElement]') OK
+EXPECTED (document.defaultView.getComputedStyle(span, null).getPropertyValue('background-color') == 'rgb(0, 255, 0)') OK
+EXPECTED (document.defaultView.getComputedStyle(document.documentElement, null).getPropertyValue('background-color') == 'rgb(255, 0, 0)') OK
+EXPECTED (document.defaultView.getComputedStyle(document.documentElement, null).getPropertyValue('color') == 'rgb(0, 0, 255)') OK
 END OF TEST
 

third_party/WebKit/LayoutTests/fullscreen/full-screen-css.html

@@ -18,33 +18,32 @@
             if (callback)
                 callback(event)
         };
-        waitForEvent(document, 'webkitfullscreenchange', fullscreenChanged);
+        waitForEvent(document, "webkitfullscreenchange", fullscreenChanged);
+
+        var span = document.getElementsByTagName("span")[0];
 
-        var span = document.getElementsByTagName('span')[0];
-    
         testExpected("document.defaultView.getComputedStyle(span, null).getPropertyValue('background-color')", "rgba(0, 0, 0, 0)");
         testExpected("document.defaultView.getComputedStyle(document.documentElement, null).getPropertyValue('background-color')", "rgba(0, 0, 0, 0)");
         testExpected("document.defaultView.getComputedStyle(document.documentElement, null).getPropertyValue('color')", "rgb(0, 0, 0)");
-    
-        var spanEnteredFullScreen = function(event) {
-            testExpected("document.webkitCurrentFullScreenElement", span);
-            testExpected("document.defaultView.getComputedStyle(span, null).getPropertyValue('background-color')", "rgb(0, 255, 0)");
-            testExpected("document.defaultView.getComputedStyle(document.documentElement, null).getPropertyValue('background-color')", "rgb(255, 0, 0)");
-            testExpected("document.defaultView.getComputedStyle(document.documentElement, null).getPropertyValue('color')", "rgb(0, 0, 255)");
-        
-            callback = documentEnteredFullScreen;
-            runWithKeyDown(function(){document.documentElement.webkitRequestFullScreen()});
-        };
-    
+
         var documentEnteredFullScreen = function(event) {
             testExpected("document.webkitCurrentFullScreenElement", document.documentElement);
             testExpected("document.defaultView.getComputedStyle(span, null).getPropertyValue('background-color')", "rgba(0, 0, 0, 0)");
             testExpected("document.defaultView.getComputedStyle(document.documentElement, null).getPropertyValue('background-color')", "rgb(0, 255, 0)");
             testExpected("document.defaultView.getComputedStyle(document.documentElement, null).getPropertyValue('color')", "rgb(0, 0, 255)");
+            callback = spanEnteredFullScreen;
+            runWithKeyDown(function(){span.webkitRequestFullScreen()});
+        };
+
+         var spanEnteredFullScreen = function(event) {
+            testExpected("document.webkitCurrentFullScreenElement", span);
+            testExpected("document.defaultView.getComputedStyle(span, null).getPropertyValue('background-color')", "rgb(0, 255, 0)");
+            testExpected("document.defaultView.getComputedStyle(document.documentElement, null).getPropertyValue('background-color')", "rgb(255, 0, 0)");
+            testExpected("document.defaultView.getComputedStyle(document.documentElement, null).getPropertyValue('color')", "rgb(0, 0, 255)");
             endTest();
         };
-    
-        callback = spanEnteredFullScreen;
-        runWithKeyDown(function(){span.webkitRequestFullScreen()});
+
+        callback = documentEnteredFullScreen;
+        runWithKeyDown(function(){document.documentElement.webkitRequestFullScreen()});
     }
 </script>

third_party/WebKit/LayoutTests/fullscreen/full-screen-twice-expected.txt

 EVENT(webkitfullscreenchange)
 EXPECTED (document.webkitCurrentFullScreenElement == '[object HTMLSpanElement]') OK
-EVENT(webkitfullscreenchange)
-EXPECTED (document.webkitCurrentFullScreenElement == '[object HTMLHtmlElement]') OK
+EVENT(webkitfullscreenerror)
 END OF TEST
 

third_party/WebKit/LayoutTests/fullscreen/full-screen-twice.html

@@ -7,29 +7,15 @@
         logResult(false, "Element.prototype.webkitRequestFullScreen == undefined");
         endTest();
     } else {
-        var callback;
-        var fullscreenChanged = function(event)
-        {
-            if (callback)
-                callback(event)
-        };
-        waitForEvent(document, 'webkitfullscreenchange', fullscreenChanged);
-    
-        var span = document.getElementsByTagName('span')[0];
+        var span = document.getElementsByTagName("span")[0];
 
         var spanEnteredFullScreen = function() {
             testExpected("document.webkitCurrentFullScreenElement", span);
-            callback = documentEnteredFullScreen;
+            waitForEventAndEnd(document, "webkitfullscreenerror");
             runWithKeyDown(function(){document.documentElement.webkitRequestFullScreen()});
         };
-    
-        var documentEnteredFullScreen = function() {
-            testExpected("document.webkitCurrentFullScreenElement", document.documentElement);
-            callback = null;
-            endTest();
-        };
 
-        callback = spanEnteredFullScreen;
+        waitForEvent(document, "webkitfullscreenchange", spanEnteredFullScreen);
         runWithKeyDown(function(){span.webkitRequestFullScreen()});
     }
 </script>

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

@@ -186,15 +186,11 @@ bool FullscreenElementStack::elementReady(Element& element, RequestType requestT
             return false;
     }
 
-    // element's node document fullscreen element stack is either empty or its top element is an
+    // element's node document's fullscreen element stack is either empty or its top element is an
     // ancestor of element.
-    if (Element* lastElementOnStack = fullscreenElementFrom(element.document())) {
-        if (!element.isDescendantOf(lastElementOnStack)) {
-            if (requestType == PrefixedMozillaRequest || requestType == PrefixedMozillaAllowKeyboardInputRequest)
-                UseCounter::count(element.document(), UseCounter::LegacyFullScreenErrorExemption);
-            else
-                return false;
-        }
+    if (Element* topElement = fullscreenElementFrom(element.document())) {
+        if (!element.isDescendantOf(topElement))
+            return false;
     }
 
     // element has no ancestor element whose local name is iframe and namespace is the HTML

third_party/WebKit/Source/core/frame/UseCounter.h

@@ -453,7 +453,6 @@ public:
         KeyEventNotAllowedInFullScreen = 474,
         DOMWindowOpen = 475,
         DOMWindowOpenFeatures = 476,
-        LegacyFullScreenErrorExemption = 477,
         MediaStreamTrackGetSources = 478,
         AspectRatioFlexItem = 479,
         DetailsElement = 480,