Adding backgroundColor to WebCompositionUnderline and using it for InlineTextBox drawing.

Source/core/editing/CompositionUnderlineRangeFilter.cpp

Index: Source/core/editing/CompositionUnderlineRangeFilter.cpp
diff --git a/Source/core/editing/CompositionUnderlineRangeFilter.cpp b/Source/core/editing/CompositionUnderlineRangeFilter.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..79eabf13d51518b68072f545921572f4ce71bdb3
--- /dev/null
+++ b/Source/core/editing/CompositionUnderlineRangeFilter.cpp
@@ -0,0 +1,33 @@
+// 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.
+
+#include "config.h"
+#include "core/editing/CompositionUnderlineRangeFilter.h"
+
+namespace WebCore {
+
+size_t CompositionUnderlineRangeFilter::seekValidIndex(size_t index)
+{
+    if (index == kNotFound)
+        return kNotFound;
+
+    size_t numUnderlines = m_underlines.size();
+    while (static_cast<size_t>(index) < numUnderlines) {
+        const CompositionUnderline& underline = m_underlines[index];
+
+        if (underline.endOffset <= m_indexLo) {
+            // |underline| is completely before the query range: keep on looking.
+            ++index;
+        } else if (underline.startOffset <= m_indexHi) {
+            // |underline| intersects with the query range: found valid and return.
+            return index;
+        } else {
+            // |underline| is completely after the query range: bail.
+            break;
+        }
+    }
+    return kNotFound;
+}
+
+} // namespace WebCore