WebGL: Free temporary GPU resources held by inactive or hidden WebGL.

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 767fcfdbff1c091bbb348c01d841da384e902627..dfca67a44f8e970bc8ca6a94fff11c1b5f542f65 100644
--- a/Source/platform/graphics/gpu/DrawingBufferTest.cpp
+++ b/Source/platform/graphics/gpu/DrawingBufferTest.cpp
@@ -620,4 +620,25 @@ TEST(DrawingBufferDepthStencilTest, packedDepthStencilSupported)
     }
 }
 
+TEST_F(DrawingBufferTest, verifySetIsHiddenProperlyAffectsMailboxes)
+{
+    blink::WebExternalTextureMailbox mailbox;
+
+    // Produce mailboxes.
+    m_drawingBuffer->markContentsChanged();
+    EXPECT_TRUE(m_drawingBuffer->prepareMailbox(&mailbox, 0));
+
+    unsigned waitSyncPoint = webContext()->insertSyncPoint();
+    mailbox.syncPoint = waitSyncPoint;
+    m_drawingBuffer->setIsHidden(true);
+    m_drawingBuffer->mailboxReleased(mailbox);
+    // m_drawingBuffer deletes mailbox immediately when hidden.
+    EXPECT_EQ(waitSyncPoint, webContext()->mostRecentlyWaitedSyncPoint());
+
+    // Fails to get mailbox when hidden.
+    EXPECT_FALSE(m_drawingBuffer->prepareMailbox(&mailbox, 0));
+
+    m_drawingBuffer->beginDestruction();
+}
+
 } // namespace