Adding backgroundColor to WebCompositionUnderline and using it for InlineTextBox drawing.

Source/core/editing/CompositionUnderlineRangeFilter.h

Index: Source/core/editing/CompositionUnderlineRangeFilter.h
diff --git a/Source/core/editing/CompositionUnderlineRangeFilter.h b/Source/core/editing/CompositionUnderlineRangeFilter.h
new file mode 100644
index 0000000000000000000000000000000000000000..c3093db04b4957a5860d239741abd5b73c551380
--- /dev/null
+++ b/Source/core/editing/CompositionUnderlineRangeFilter.h
@@ -0,0 +1,78 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CompositionUnderlineRangeFilter_h
+#define CompositionUnderlineRangeFilter_h
+
+#include "core/editing/CompositionUnderline.h"
+#include "wtf/NotFound.h"
+#include "wtf/Vector.h"
+
+namespace WebCore {
+
+// A visitor class to yield elements of a sorted (by startOffset) list of
+// underlines, visiting only elements that intersect with specified *inclusive*
+// range [indexLo, indexHi].
+class CompositionUnderlineRangeFilter {
+    WTF_MAKE_NONCOPYABLE(CompositionUnderlineRangeFilter);
+public:
+    class ConstIterator {
+    public:
+        ConstIterator(): m_filter(nullptr), m_index(0) { }
+        const CompositionUnderline& operator*()
+        {
+            ASSERT(m_index != kNotFound);
+            return m_filter->m_underlines[m_index];
+        }
+        ConstIterator& operator++()
+        {
+            if (m_index != kNotFound)
+                m_index = m_filter->seekValidIndex(m_index + 1);
+            return *this;
+        }
+        const CompositionUnderline* operator->()
+        {
+            ASSERT(m_index != kNotFound);
+            return &m_filter->m_underlines[m_index];
+        }
+        bool operator==(const ConstIterator& other)
+        {
+            return other.m_index == m_index && other.m_filter == m_filter;
+        }
+        bool operator!=(const ConstIterator& other) { return !operator==(other); }
+
+    private:
+        friend class CompositionUnderlineRangeFilter;
+
+        ConstIterator(CompositionUnderlineRangeFilter* filter, size_t index)
+            : m_filter(filter)
+            , m_index(index) { }
+        CompositionUnderlineRangeFilter* m_filter;
+        size_t m_index;
+    };
+
+    CompositionUnderlineRangeFilter(const Vector<CompositionUnderline>& underlines, size_t indexLo, size_t indexHi);
+
+    ConstIterator begin() { return ConstIterator(this, seekValidIndex(0)); }
+    const ConstIterator& end() { return m_theEnd; }
+
+private:
+    friend class ConstIterator;
+
+    // Returns |index| if |m_underlines[index]| intersects with range
+    // [m_indexLo, m_indexHi]. Otherwise returns the index of the next
+    // intersecting interval, or END if there are none left.
+    size_t seekValidIndex(size_t index);
+
+    // Assume that elements of |m_underlines| are sorted by |.startOffset|.
+    const Vector<CompositionUnderline>& m_underlines;
+    // The "query range" is the inclusive range [m_indexLo, m_indexHi].
+    const size_t m_indexLo;
+    const size_t m_indexHi;
+    const ConstIterator m_theEnd;
+};
+
+} // namespace WebCore
+
+#endif