Use std::map to find correct index range

Instead of iterating through every range to find the one we're looking for, instead put them all in a map and find them with that. This helps performance with index buffers that contain a bunch of different ranges.

BUG=
TEST=

Review URL: http://codereview.appspot.com/4974051

git-svn-id: https://angleproject.googlecode.com/svn/trunk@742 736b8ea6-26fd-11df-bfd4-992fa37f6226
diff --git a/src/libGLESv2/IndexDataManager.h b/src/libGLESv2/IndexDataManager.h
index 814f410..c076b90 100644
--- a/src/libGLESv2/IndexDataManager.h
+++ b/src/libGLESv2/IndexDataManager.h
@@ -87,12 +87,28 @@
         intptr_t offset;
         GLsizei count;
 
+        bool operator<(const IndexRange& rhs) const
+        {
+            if (offset != rhs.offset)
+            {
+                return offset < rhs.offset;
+            }
+            if (count != rhs.count)
+            {
+                return count < rhs.count;
+            }
+            return false;
+        }
+    };
+
+    struct IndexResult
+    {
         UINT minIndex;
         UINT maxIndex;
         UINT streamOffset;
     };
 
-    std::vector<IndexRange> mCache;
+    std::map<IndexRange, IndexResult> mCache;
 };
 
 class IndexDataManager