Fix MQEvaluator::mediaType() related perf regressions.

When we stopped storing the mediaType as a string on m_medium on StyleResolver, 
we started calling FrameView::mediaType() every time that the mediaType as required.
In the related bug's test case, mediaType() was being called a lot, 
in order to compare it to "print" to see which default style sheet should be used.
Since mediaType() calls also call InspectorInstrumentation::applyEmulatedMedia(), 
they have a certain overhead, that impacted the benchmark's results.

I've changed it so that the mediaType() call and the comparison to "print"
would be done once, and the result cached.

BUG=394275

Review URL: https://codereview.chromium.org/405953002

git-svn-id: svn://svn.chromium.org/blink/trunk@179991 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/core/css/MediaQueryEvaluator.cpp

@@ -111,15 +111,6 @@ bool MediaQueryEvaluator::mediaTypeMatch(const String& mediaTypeToMatch) const
         || equalIgnoringCase(mediaTypeToMatch, mediaType());
 }
 
-bool MediaQueryEvaluator::mediaTypeMatchSpecific(const char* mediaTypeToMatch) const
-{
-    // Like mediaTypeMatch, but without the special cases for "" and "all".
-    ASSERT(mediaTypeToMatch);
-    ASSERT(mediaTypeToMatch[0] != '\0');
-    ASSERT(!equalIgnoringCase(mediaTypeToMatch, MediaTypeNames::all));
-    return equalIgnoringCase(mediaTypeToMatch, mediaType());
-}
-
 static bool applyRestrictor(MediaQuery::Restrictor r, bool value)
 {
     return r == MediaQuery::Not ? !value : value;

third_party/WebKit/Source/core/css/MediaQueryEvaluator.h

@@ -68,15 +68,14 @@ public:
     MediaQueryEvaluator(const char* acceptedMediaType, bool mediaFeatureResult = false);
 
     // Creates evaluator which evaluates full media queries
-    MediaQueryEvaluator(LocalFrame*);
+    explicit MediaQueryEvaluator(LocalFrame*);
 
     // Creates evaluator which evaluates in a thread-safe manner a subset of media values
-    MediaQueryEvaluator(const MediaValues&);
+    explicit MediaQueryEvaluator(const MediaValues&);
 
     ~MediaQueryEvaluator();
 
     bool mediaTypeMatch(const String& mediaTypeToMatch) const;
-    bool mediaTypeMatchSpecific(const char* mediaTypeToMatch) const;
 
     // Evaluates a list of media queries
     bool eval(const MediaQuerySet*, MediaQueryResultList* = 0) const;

third_party/WebKit/Source/core/css/resolver/StyleResolver.cpp

@@ -31,6 +31,7 @@
 
 #include "core/CSSPropertyNames.h"
 #include "core/HTMLNames.h"
+#include "core/MediaTypeNames.h"
 #include "core/StylePropertyShorthand.h"
 #include "core/animation/ActiveAnimations.h"
 #include "core/animation/Animation.h"
@@ -132,16 +133,19 @@ StyleResolver::StyleResolver(Document& document)
     : m_document(document)
     , m_viewportStyleResolver(ViewportStyleResolver::create(&document))
     , m_needCollectFeatures(false)
+    , m_printMediaType(false)
     , m_styleResourceLoader(document.fetcher())
     , m_styleSharingDepth(0)
     , m_styleResolverStatsSequence(0)
     , m_accessCount(0)
 {
     FrameView* view = document.view();
-    if (view)
+    if (view) {
         m_medium = adoptPtr(new MediaQueryEvaluator(&view->frame()));
-    else
+        m_printMediaType = equalIgnoringCase(view->mediaType(), MediaTypeNames::print);
+    } else {
         m_medium = adoptPtr(new MediaQueryEvaluator("all"));
+    }
 
     initWatchedSelectorRules(CSSSelectorWatch::from(document).watchedCallbackSelectors());
 
@@ -456,8 +460,7 @@ void StyleResolver::matchUARules(ElementRuleCollector& collector)
     collector.setMatchingUARules(true);
 
     CSSDefaultStyleSheets& defaultStyleSheets = CSSDefaultStyleSheets::instance();
-    RuleSet* userAgentStyleSheet = m_medium->mediaTypeMatchSpecific("print")
-        ? defaultStyleSheets.defaultPrintStyle() : defaultStyleSheets.defaultStyle();
+    RuleSet* userAgentStyleSheet = m_printMediaType ? defaultStyleSheets.defaultPrintStyle() : defaultStyleSheets.defaultStyle();
     matchUARules(collector, userAgentStyleSheet);
 
     // In quirks mode, we match rules from the quirks user agent sheet.

third_party/WebKit/Source/core/css/resolver/StyleResolver.h

@@ -305,6 +305,7 @@ private:
     TreeBoundaryCrossingRules m_treeBoundaryCrossingRules;
 
     bool m_needCollectFeatures;
+    bool m_printMediaType;
 
     StyleResourceLoader m_styleResourceLoader;