Display MathML fallback content when it is specified and take into account inline/display modes for…

Source/core/css/CSSDefaultStyleSheets.cpp

Index: Source/core/css/CSSDefaultStyleSheets.cpp
diff --git a/Source/core/css/CSSDefaultStyleSheets.cpp b/Source/core/css/CSSDefaultStyleSheets.cpp
index 9375aa4b8e4026fd2d8d31db74cb10e4dfb1721e..c549efc6f34b4e7ea643264ee1e0b25fd41dc257 100644
--- a/Source/core/css/CSSDefaultStyleSheets.cpp
+++ b/Source/core/css/CSSDefaultStyleSheets.cpp
@@ -29,6 +29,7 @@
 #include "config.h"
 #include "core/css/CSSDefaultStyleSheets.h"
 
+#include "MathMLNames.h"
 #include "UserAgentStyleSheets.h"
 #include "core/css/MediaQueryEvaluator.h"
 #include "core/css/RuleSet.h"
@@ -53,6 +54,7 @@ StyleSheetContents* CSSDefaultStyleSheets::defaultStyleSheet;
 StyleSheetContents* CSSDefaultStyleSheets::viewportStyleSheet;
 StyleSheetContents* CSSDefaultStyleSheets::quirksStyleSheet;
 StyleSheetContents* CSSDefaultStyleSheets::svgStyleSheet;
+StyleSheetContents* CSSDefaultStyleSheets::mathmlStyleSheet;
 StyleSheetContents* CSSDefaultStyleSheets::mediaControlsStyleSheet;
 StyleSheetContents* CSSDefaultStyleSheets::fullscreenStyleSheet;
 
@@ -141,6 +143,16 @@ void CSSDefaultStyleSheets::ensureDefaultStyleSheetsForElement(Element* element,
         changedDefaultStyle = true;
     }
 
+    // FIXME: We should assert that the sheet only styles MathML elements.
+    if (element->namespaceURI() == MathMLNames::mathmlNamespaceURI
+    && !mathmlStyleSheet) {
+        mathmlStyleSheet = parseUASheet(mathmlUserAgentStyleSheet,
+    sizeof(mathmlUserAgentStyleSheet));
+        defaultStyle->addRulesFromSheet(mathmlStyleSheet, screenEval());
+        defaultPrintStyle->addRulesFromSheet(mathmlStyleSheet, printEval());
+        changedDefaultStyle = true;
+    }
+
     // FIXME: We should assert that this sheet only contains rules for <video> and <audio>.
     if (!mediaControlsStyleSheet && (element->hasTagName(videoTag) || element->hasTagName(audioTag))) {
         String mediaRules = String(mediaControlsUserAgentStyleSheet, sizeof(mediaControlsUserAgentStyleSheet)) + RenderTheme::theme().extraMediaControlsStyleSheet();