Let canvas decide how to handle the lost resource: WebGL part

Source/platform/graphics/gpu/DrawingBufferTest.cpp

Index: Source/platform/graphics/gpu/DrawingBufferTest.cpp
diff --git a/Source/platform/graphics/gpu/DrawingBufferTest.cpp b/Source/platform/graphics/gpu/DrawingBufferTest.cpp
index 437629396ecd825fda31b093c327420a9d2ea2c6..bb57c9482b1d4ece545f9b5d4d66eecff8fdbb03 100644
--- a/Source/platform/graphics/gpu/DrawingBufferTest.cpp
+++ b/Source/platform/graphics/gpu/DrawingBufferTest.cpp
@@ -315,6 +315,41 @@ TEST_F(DrawingBufferTest, verifyDestructionCompleteAfterAllMailboxesReleased)
     EXPECT_EQ(live, false);
 }
 
+TEST_F(DrawingBufferTest, verifyDrawingBufferStaysAliveIfResourcesAreLost)
+{
+    bool live = true;
+    m_drawingBuffer->m_live = &live;
+    blink::WebExternalTextureMailbox mailbox1;
+    blink::WebExternalTextureMailbox mailbox2;
+    blink::WebExternalTextureMailbox mailbox3;
+
+    m_drawingBuffer->markContentsChanged();
+    EXPECT_TRUE(m_drawingBuffer->prepareMailbox(&mailbox1, 0));
+    m_drawingBuffer->markContentsChanged();
+    EXPECT_TRUE(m_drawingBuffer->prepareMailbox(&mailbox2, 0));
+    m_drawingBuffer->markContentsChanged();
+    EXPECT_TRUE(m_drawingBuffer->prepareMailbox(&mailbox3, 0));
+
+    m_drawingBuffer->markContentsChanged();
+    m_drawingBuffer->mailboxReleased(mailbox1, true);
+    EXPECT_EQ(live, true);
+
+    m_drawingBuffer->beginDestruction();
+    EXPECT_EQ(live, true);
+
+    m_drawingBuffer->markContentsChanged();
+    m_drawingBuffer->mailboxReleased(mailbox2, false);
+    EXPECT_EQ(live, true);
+
+    DrawingBufferForTests* weakPtr = m_drawingBuffer.get();
+    m_drawingBuffer.clear();
+    EXPECT_EQ(live, true);
+
+    weakPtr->markContentsChanged();
+    weakPtr->mailboxReleased(mailbox3, true);
+    EXPECT_EQ(live, false);
+}
+
 class TextureMailboxWrapper {
 public:
     explicit TextureMailboxWrapper(const blink::WebExternalTextureMailbox& mailbox)