Fix assertion failure during out-of-order matching

Source/platform/graphics/paint/DisplayItemListTest.cpp

Index: Source/platform/graphics/paint/DisplayItemListTest.cpp
diff --git a/Source/platform/graphics/paint/DisplayItemListTest.cpp b/Source/platform/graphics/paint/DisplayItemListTest.cpp
index 0605017cfe508fed1be79a53d4beaad56c62c3f4..5e877deff8e808298e3048d08a7f5e066be190d3 100644
--- a/Source/platform/graphics/paint/DisplayItemListTest.cpp
+++ b/Source/platform/graphics/paint/DisplayItemListTest.cpp
@@ -516,6 +516,33 @@ TEST_F(DisplayItemListTest, CachedSubsequenceSwapOrder)
         TestDisplayItem(container1, DisplayItem::EndSubsequence));
 }
 
+// Test for crbug.com/526590

[pdr., 2015/09/02 23:13:12]

No need for this or the comment "// Should not crash", as this test is clean and
easy to understand.

[Xianzhu, 2015/09/02 23:21:44]

Done.

+TEST_F(DisplayItemListTest, OutOfOrderNoCrash)
+{
+    TestDisplayItemClient client("client");
+    GraphicsContext context(&displayItemList());
+
+    const DisplayItem::Type type1 = DisplayItem::DrawingFirst;
+    const DisplayItem::Type type2 = static_cast<DisplayItem::Type>(DisplayItem::DrawingFirst + 1);
+    const DisplayItem::Type type3 = static_cast<DisplayItem::Type>(DisplayItem::DrawingFirst + 2);
+    const DisplayItem::Type type4 = static_cast<DisplayItem::Type>(DisplayItem::DrawingFirst + 3);
+
+    drawRect(context, client, type1, FloatRect(100, 100, 100, 100));
+    drawRect(context, client, type2, FloatRect(100, 100, 50, 200));
+    drawRect(context, client, type3, FloatRect(100, 100, 50, 200));
+    drawRect(context, client, type4, FloatRect(100, 100, 100, 100));
+
+    displayItemList().commitNewDisplayItems();
+
+    drawRect(context, client, type2, FloatRect(100, 100, 50, 200));
+    drawRect(context, client, type3, FloatRect(100, 100, 50, 200));
+    drawRect(context, client, type1, FloatRect(100, 100, 100, 100));
+    drawRect(context, client, type4, FloatRect(100, 100, 100, 100));
+
+    displayItemList().commitNewDisplayItems();
+    // Should not crash.
+}
+
 TEST_F(DisplayItemListTest, CachedNestedSubsequenceUpdate)
 {
     TestDisplayItemClient container1("container1");