Prepare for multiple !important author ranges.

Source/core/css/resolver/MatchResult.h

Index: Source/core/css/resolver/MatchResult.h
diff --git a/Source/core/css/resolver/MatchResult.h b/Source/core/css/resolver/MatchResult.h
index 8170d451d5f000a2093d6543a17758d4515bea2c..f87836c7874fa7a401c975d953dbeadf47a1b2fd 100644
--- a/Source/core/css/resolver/MatchResult.h
+++ b/Source/core/css/resolver/MatchResult.h
@@ -59,21 +59,94 @@ WTF_ALLOW_MOVE_AND_INIT_WITH_MEM_FUNCTIONS(blink::MatchedProperties);
 
 namespace blink {
 
+using MatchedPropertiesVector = WillBeHeapVector<MatchedProperties, 64>;
+
+// MatchedPropertiesRange is used to represent a subset of the matched properties from
+// a given origin, for instance UA rules, author rules, or a shadow tree scope. This is
+// needed because rules from different origins are applied in the opposite order for
+// !important rules, yet in the same order as for normal rules within the same origin.
+
+class MatchedPropertiesRange {
+public:
+    MatchedPropertiesRange(MatchedPropertiesVector::const_iterator begin, MatchedPropertiesVector::const_iterator end)
+        : m_begin(begin)
+        , m_end(end)
+    {
+    }
+
+    MatchedPropertiesVector::const_iterator begin() const { return m_begin; }
+    MatchedPropertiesVector::const_iterator end() const { return m_end; }
+
+private:
+    MatchedPropertiesVector::const_iterator m_begin;
+    MatchedPropertiesVector::const_iterator m_end;
+};
+
 class MatchResult {
     STACK_ALLOCATED();
 public:
     void addMatchedProperties(const StylePropertySet* properties, unsigned linkMatchType = CSSSelector::MatchAll, PropertyWhitelistType = PropertyWhitelistNone);
+    bool hasMatchedProperties() const { return m_matchedProperties.size(); }
+
+    void uaRulesFinished();

[kochi, 2015/08/11 11:07:35]

It sounds a bit strange to have "Finished" suffix as it sounds
returning a boolean value.  Actually this method changes the
internal state of MatchedResult object, so verb+noun sounds
better (note: I'm not a native English speaker) to me.

What about finishAddingUARules()?

[rune, 2015/08/12 01:13:26]

Done.

+    void authorScopeFinished();

[kochi, 2015/08/11 11:07:35]

Ditto, and why "Scope", not "Rules"?

What about finishAddingAuthorRules()?

[rune, 2015/08/12 01:13:26]

Done.

+
+    void setIsCacheable(bool cacheable) { m_isCacheable = cacheable; }
+    bool isCacheable() const { return m_isCacheable; }
+
+    MatchedPropertiesRange allRules() const { return MatchedPropertiesRange(m_matchedProperties.begin(), m_matchedProperties.end()); }
+    MatchedPropertiesRange uaRules() const { return MatchedPropertiesRange(m_matchedProperties.begin(), m_matchedProperties.begin() + m_uaRangeEnd); }
+    MatchedPropertiesRange authorRules() const { return MatchedPropertiesRange(m_matchedProperties.begin() + m_uaRangeEnd, m_matchedProperties.end()); }
+
+    const MatchedPropertiesVector& matchedProperties() const { return m_matchedProperties; }
+
+private:
+    friend class ImportantAuthorRanges;
+    friend class ImportantAuthorRangeIterator;
+
+    MatchedPropertiesVector m_matchedProperties;
+    Vector<unsigned, 16> m_authorRangeEnd;

[kochi, 2015/08/11 11:07:35]

At first I was confused why m_uaRangeEnd is a scaler while m_authorRangeEnd
is a vector.  Maybe m_authorRangeEnds?

[rune, 2015/08/12 01:13:26]

Done.

+    unsigned m_uaRangeEnd = 0;
+    bool m_isCacheable = true;
+};
+
+class ImportantAuthorRangeIterator {
+public:
+    ImportantAuthorRangeIterator(const MatchResult& result, int endIndex)
+        : m_result(result)
+        , m_endIndex(endIndex) { }
+
+    MatchedPropertiesRange operator*() const
+    {
+        ASSERT(m_endIndex >= 0);
+        unsigned rangeEnd = m_result.m_authorRangeEnd[m_endIndex];
+        unsigned rangeBegin = m_endIndex ? m_result.m_authorRangeEnd[m_endIndex - 1] : m_result.m_uaRangeEnd;
+        return MatchedPropertiesRange(m_result.matchedProperties().begin() + rangeBegin, m_result.matchedProperties().begin() + rangeEnd);
+    }
+
+    ImportantAuthorRangeIterator& operator++()
+    {
+        ASSERT(m_endIndex >= 0);
+        --m_endIndex;
+        return *this;
+    }
+
+    bool operator!=(const ImportantAuthorRangeIterator& other) const { return m_endIndex != other.m_endIndex || &m_result != &other.m_result; }
+
+private:
+    const MatchResult& m_result;
+    unsigned m_endIndex;
+};
+
+class ImportantAuthorRanges {
+public:
+    explicit ImportantAuthorRanges(const MatchResult& result) : m_result(result) { }
 
-    unsigned begin() const { return 0; }
-    unsigned end() const { return matchedProperties.size(); }
-    unsigned beginUA() const { return 0; }
-    unsigned endUA() const { return uaEnd; }
-    unsigned beginAuthor() const { return uaEnd; }
-    unsigned endAuthor() const { return matchedProperties.size(); }
+    ImportantAuthorRangeIterator begin() const { return ImportantAuthorRangeIterator(m_result, m_result.m_authorRangeEnd.size() - 1); }
+    ImportantAuthorRangeIterator end() const { return ImportantAuthorRangeIterator(m_result, -1); }
 
-    WillBeHeapVector<MatchedProperties, 64> matchedProperties;
-    unsigned uaEnd = 0;
-    bool isCacheable = true;
+private:
+    const MatchResult& m_result;
 };
 
 inline bool operator==(const MatchedProperties& a, const MatchedProperties& b)