Fix crash on exit of Google Maps

QtWebKit may crash when exiting the new WebGL version of Google maps.

The problem is that under some circumstances the PlatformLayer is destroyed
before the GraphicsLayer that reference it, causing the GraphicsLayer to
access it during destruction.

Change-Id: Ia3d0f337dcb9b8b38e9e23f53bea669bd868f713
Reviewed-by: Jocelyn Turcotte <jocelyn.turcotte@digia.com>

3 files changed, 7 insertions, 0 deletions

diff --git a/Source/WebCore/platform/graphics/qt/GraphicsContext3DQt.cpp b/Source/WebCore/platform/graphics/qt/GraphicsContext3DQt.cpp
index 1c7289cec..9824eb55f 100644
--- a/Source/WebCore/platform/graphics/qt/GraphicsContext3DQt.cpp
+++ b/Source/WebCore/platform/graphics/qt/GraphicsContext3DQt.cpp
@@ -221,6 +221,10 @@ void GraphicsContext3DPrivate::initializeANGLE()
 
 GraphicsContext3DPrivate::~GraphicsContext3DPrivate()
 {
+#if USE(ACCELERATED_COMPOSITING)
+    if (TextureMapperPlatformLayer::Client* client = TextureMapperPlatformLayer::client())
+        client->platformLayerWasDestroyed();
+#endif
     delete m_surfaceOwner;
     m_surfaceOwner = 0;
 }
diff --git a/Source/WebCore/platform/graphics/texmap/GraphicsLayerTextureMapper.h b/Source/WebCore/platform/graphics/texmap/GraphicsLayerTextureMapper.h
index 61ddfb92a..16e4ebad0 100644
--- a/Source/WebCore/platform/graphics/texmap/GraphicsLayerTextureMapper.h
+++ b/Source/WebCore/platform/graphics/texmap/GraphicsLayerTextureMapper.h
@@ -112,7 +112,9 @@ private:
     void prepareBackingStoreIfNeeded();
     bool shouldHaveBackingStore() const;
 
+    // TextureMapperPlatformLayer::Client methods:
     virtual void setPlatformLayerNeedsDisplay() OVERRIDE { setContentsNeedsDisplay(); }
+    virtual void platformLayerWasDestroyed() OVERRIDE { m_contentsLayer = 0; }
 
     // This set of flags help us defer which properties of the layer have been
     // modified by the compositor, so we can know what to look for in the next flush.
diff --git a/Source/WebCore/platform/graphics/texmap/TextureMapperPlatformLayer.h b/Source/WebCore/platform/graphics/texmap/TextureMapperPlatformLayer.h
index 0cab98da4..e0888766a 100644
--- a/Source/WebCore/platform/graphics/texmap/TextureMapperPlatformLayer.h
+++ b/Source/WebCore/platform/graphics/texmap/TextureMapperPlatformLayer.h
@@ -34,6 +34,7 @@ public:
     class Client {
     public:
         virtual void setPlatformLayerNeedsDisplay() = 0;
+        virtual void platformLayerWasDestroyed() = 0;
     };
 
     TextureMapperPlatformLayer() : m_client(0) { }