WebGL: Transfer ownership of WebGraphicsContext3D from WebGLRenderingContext to DrawingBuffer.

Currently, the lifecycle of DrawingBuffer is different from it of
WebGraphicsContext3D, so there is so many checks if the context is valid.
This complexity is not necessary because DrawingBuffer does not own any
objects when the context is lost or impossible to be created.

To be clear the lifecycle, this CL makes DrawingBuffer take ownership of WebGraphicsContext3D.

The DrawingBuffer creation or resize can fail if the memory is not enough. This
logic is preserved.
In detail,
1. If it occurs during WebGLRenderingContext creation, we give up creating
WebGLRenderingContext.
2. If it occurs during restoration of lost context, we will try again.
3. If it occurs during resizing DrawingBuffer, we slightly ignore, because we
can reuse different size FBO in this case.

In addition, this CL fixes two bugs.
1. maybeRestoreContext() pretends to success to restore although creating FBO in
DrawingBuffer fails. As mentioned earlier, we will try again.
2. WebGLRenderingContext calls DrawingBuffer::reset() twice during creation,
because the constructor of DrawingBuffer internally calls reset().

BUG=344393

Review URL: https://codereview.chromium.org/163773007

git-svn-id: svn://svn.chromium.org/blink/trunk@168457 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/core/html/canvas/OESVertexArrayObject.cpp

@@ -72,7 +72,7 @@ void OESVertexArrayObject::deleteVertexArrayOES(WebGLVertexArrayObjectOES* array
     if (!arrayObject->isDefaultObject() && arrayObject == m_context->m_boundVertexArrayObject)
         m_context->setBoundVertexArrayObject(nullptr);
 
-    arrayObject->deleteObject(m_context->webGraphicsContext3D());
+    arrayObject->deleteObject(m_context->webContext());
 }
 
 GLboolean OESVertexArrayObject::isVertexArrayOES(WebGLVertexArrayObjectOES* arrayObject)
@@ -83,7 +83,7 @@ GLboolean OESVertexArrayObject::isVertexArrayOES(WebGLVertexArrayObjectOES* arra
     if (!arrayObject->hasEverBeenBound())
         return 0;
 
-    return m_context->webGraphicsContext3D()->isVertexArrayOES(arrayObject->object());
+    return m_context->webContext()->isVertexArrayOES(arrayObject->object());
 }
 
 void OESVertexArrayObject::bindVertexArrayOES(WebGLVertexArrayObjectOES* arrayObject)
@@ -92,17 +92,17 @@ void OESVertexArrayObject::bindVertexArrayOES(WebGLVertexArrayObjectOES* arrayOb
         return;
 
     if (arrayObject && (arrayObject->isDeleted() || !arrayObject->validate(0, context()))) {
-        m_context->webGraphicsContext3D()->synthesizeGLError(GL_INVALID_OPERATION);
+        m_context->webContext()->synthesizeGLError(GL_INVALID_OPERATION);
         return;
     }
 
     if (arrayObject && !arrayObject->isDefaultObject() && arrayObject->object()) {
-        m_context->webGraphicsContext3D()->bindVertexArrayOES(arrayObject->object());
+        m_context->webContext()->bindVertexArrayOES(arrayObject->object());
 
         arrayObject->setHasEverBeenBound();
         m_context->setBoundVertexArrayObject(arrayObject);
     } else {
-        m_context->webGraphicsContext3D()->bindVertexArrayOES(0);
+        m_context->webContext()->bindVertexArrayOES(0);
         m_context->setBoundVertexArrayObject(nullptr);
     }
 }

third_party/WebKit/Source/core/html/canvas/WebGLBuffer.cpp

@@ -41,7 +41,7 @@ WebGLBuffer::WebGLBuffer(WebGLRenderingContextBase* ctx)
     , m_target(0)
 {
     ScriptWrappable::init(this);
-    setObject(ctx->webGraphicsContext3D()->createBuffer());
+    setObject(ctx->webContext()->createBuffer());
 }
 
 WebGLBuffer::~WebGLBuffer()

third_party/WebKit/Source/core/html/canvas/WebGLContextGroup.cpp

@@ -50,7 +50,7 @@ blink::WebGraphicsContext3D* WebGLContextGroup::getAWebGraphicsContext3D()
 {
     ASSERT(!m_contexts.isEmpty());
     HashSet<WebGLRenderingContextBase*>::iterator it = m_contexts.begin();
-    return (*it)->webGraphicsContext3D();
+    return (*it)->webContext();
 }
 
 void WebGLContextGroup::addContext(WebGLRenderingContextBase* context)

third_party/WebKit/Source/core/html/canvas/WebGLContextObject.cpp

@@ -47,7 +47,7 @@ void WebGLContextObject::detachContext()
 {
     detach();
     if (m_context) {
-        deleteObject(m_context->webGraphicsContext3D());
+        deleteObject(m_context->webContext());
         m_context->removeContextObject(this);
         m_context = 0;
     }
@@ -55,7 +55,7 @@ void WebGLContextObject::detachContext()
 
 blink::WebGraphicsContext3D* WebGLContextObject::getAWebGraphicsContext3D() const
 {
-    return m_context ? m_context->webGraphicsContext3D() : 0;
+    return m_context ? m_context->webContext() : 0;
 }
 
 }

third_party/WebKit/Source/core/html/canvas/WebGLDebugShaders.cpp

@@ -58,7 +58,7 @@ String WebGLDebugShaders::getTranslatedShaderSource(WebGLShader* shader)
         return String();
     if (!m_context->validateWebGLObject("getTranslatedShaderSource", shader))
         return "";
-    return m_context->webGraphicsContext3D()->getTranslatedShaderSourceANGLE(shader->object());
+    return m_context->webContext()->getTranslatedShaderSourceANGLE(shader->object());
 }
 
 bool WebGLDebugShaders::supported(WebGLRenderingContextBase* context)

third_party/WebKit/Source/core/html/canvas/WebGLDrawBuffers.cpp

@@ -79,7 +79,7 @@ void WebGLDrawBuffers::drawBuffersWEBGL(const Vector<GLenum>& buffers)
         }
         // Because the backbuffer is simulated on all current WebKit ports, we need to change BACK to COLOR_ATTACHMENT0.
         GLenum value = (bufs[0] == GL_BACK) ? GL_COLOR_ATTACHMENT0 : GL_NONE;
-        m_context->webGraphicsContext3D()->drawBuffersEXT(1, &value);
+        m_context->webContext()->drawBuffersEXT(1, &value);
         m_context->setBackDrawBuffer(bufs[0]);
     } else {
         if (n > m_context->maxDrawBuffers()) {
@@ -99,7 +99,7 @@ void WebGLDrawBuffers::drawBuffersWEBGL(const Vector<GLenum>& buffers)
 // static
 bool WebGLDrawBuffers::satisfiesWebGLRequirements(WebGLRenderingContextBase* webglContext)
 {
-    blink::WebGraphicsContext3D* context = webglContext->webGraphicsContext3D();
+    blink::WebGraphicsContext3D* context = webglContext->webContext();
     Extensions3DUtil* extensionsUtil = webglContext->extensionsUtil();
 
     // This is called after we make sure GL_EXT_draw_buffers is supported.

third_party/WebKit/Source/core/html/canvas/WebGLFramebuffer.cpp

@@ -263,7 +263,7 @@ WebGLFramebuffer::WebGLFramebuffer(WebGLRenderingContextBase* ctx)
     , m_hasEverBeenBound(false)
 {
     ScriptWrappable::init(this);
-    setObject(ctx->webGraphicsContext3D()->createFramebuffer());
+    setObject(ctx->webContext()->createFramebuffer());
 }
 
 WebGLFramebuffer::~WebGLFramebuffer()
@@ -302,7 +302,7 @@ void WebGLFramebuffer::attach(GLenum attachment, GLenum attachmentPoint)
     ASSERT(isBound());
     WebGLAttachment* attachmentObject = getAttachment(attachment);
     if (attachmentObject)
-        attachmentObject->attach(context()->webGraphicsContext3D(), attachmentPoint);
+        attachmentObject->attach(context()->webContext(), attachmentPoint);
 }
 
 WebGLSharedObject* WebGLFramebuffer::getAttachmentObject(GLenum attachment) const
@@ -413,7 +413,7 @@ void WebGLFramebuffer::removeAttachmentFromBoundFramebuffer(GLenum attachment)
 
     WebGLAttachment* attachmentObject = getAttachment(attachment);
     if (attachmentObject) {
-        attachmentObject->onDetached(context()->webGraphicsContext3D());
+        attachmentObject->onDetached(context()->webContext());
         m_attachments.remove(attachment);
         drawBuffersIfNecessary(false);
         switch (attachment) {
@@ -446,7 +446,7 @@ void WebGLFramebuffer::removeAttachmentFromBoundFramebuffer(WebGLSharedObject* a
             WebGLAttachment* attachmentObject = it->value.get();
             if (attachmentObject->isSharedObject(attachment)) {
                 GLenum attachmentType = it->key;
-                attachmentObject->unattach(context()->webGraphicsContext3D(), attachmentType);
+                attachmentObject->unattach(context()->webContext(), attachmentType);
                 removeAttachmentFromBoundFramebuffer(attachmentType);
                 checkMore = true;
                 break;
@@ -601,7 +601,7 @@ void WebGLFramebuffer::drawBuffersIfNecessary(bool force)
         }
     }
     if (reset) {
-        context()->webGraphicsContext3D()->drawBuffersEXT(
+        context()->webContext()->drawBuffersEXT(
             m_filteredDrawBuffers.size(), m_filteredDrawBuffers.data());
     }
 }

third_party/WebKit/Source/core/html/canvas/WebGLProgram.cpp

@@ -43,7 +43,7 @@ WebGLProgram::WebGLProgram(WebGLRenderingContextBase* ctx)
     , m_infoValid(true)
 {
     ScriptWrappable::init(this);
-    setObject(ctx->webGraphicsContext3D()->createProgram());
+    setObject(ctx->webContext()->createProgram());
 }
 
 WebGLProgram::~WebGLProgram()

third_party/WebKit/Source/core/html/canvas/WebGLRenderbuffer.cpp

@@ -49,7 +49,7 @@ WebGLRenderbuffer::WebGLRenderbuffer(WebGLRenderingContextBase* ctx)
     , m_hasEverBeenBound(false)
 {
     ScriptWrappable::init(this);
-    setObject(ctx->webGraphicsContext3D()->createRenderbuffer());
+    setObject(ctx->webContext()->createRenderbuffer());
 }
 
 void WebGLRenderbuffer::deleteObjectImpl(blink::WebGraphicsContext3D* context3d, Platform3DObject object)

third_party/WebKit/Source/core/html/canvas/WebGLRenderingContext.cpp

@@ -94,7 +94,7 @@ PassOwnPtr<WebGLRenderingContext> WebGLRenderingContext::create(HTMLCanvasElemen
     renderingContext->registerContextExtensions();
     renderingContext->suspendIfNeeded();
 
-    if (renderingContext->m_drawingBuffer->isZeroSized()) {
+    if (!renderingContext->m_drawingBuffer) {
         canvas->dispatchEvent(WebGLContextEvent::create(EventTypeNames::webglcontextcreationerror, false, true, "Could not create a WebGL context."));
         return nullptr;
     }

third_party/WebKit/Source/core/html/canvas/WebGLRenderingContextBase.h

@@ -34,6 +34,7 @@
 #include "platform/Timer.h"
 #include "platform/graphics/GraphicsTypes3D.h"
 #include "platform/graphics/ImageBuffer.h"
+#include "platform/graphics/gpu/DrawingBuffer.h"
 #include "platform/graphics/gpu/Extensions3DUtil.h"
 #include "platform/graphics/gpu/WebGLImageConversion.h"
 #include "public/platform/WebGraphicsContext3D.h"
@@ -49,7 +50,6 @@ class WebLayer;
 namespace WebCore {
 
 class ANGLEInstancedArrays;
-class DrawingBuffer;
 class EXTFragDepth;
 class EXTTextureFilterAnisotropic;
 class ExceptionState;
@@ -204,7 +204,7 @@ public:
 
     void hint(GLenum target, GLenum mode);
     GLboolean isBuffer(WebGLBuffer*);
-    bool isContextLost();
+    bool isContextLost() const;
     GLboolean isEnabled(GLenum cap);
     GLboolean isFramebuffer(WebGLFramebuffer*);
     GLboolean isProgram(WebGLProgram*);
@@ -323,7 +323,7 @@ public:
     void forceRestoreContext();
     void loseContextImpl(LostContextMode);
 
-    blink::WebGraphicsContext3D* webGraphicsContext3D() const { return m_context.get(); }
+    blink::WebGraphicsContext3D* webContext() const { return m_drawingBuffer->context(); }
     WebGLContextGroup* contextGroup() const { return m_contextGroup.get(); }
     virtual blink::WebLayer* platformLayer() const OVERRIDE;
     Extensions3DUtil* extensionsUtil();
@@ -390,12 +390,10 @@ protected:
 
     WebGLRenderbuffer* ensureEmulatedStencilBuffer(GLenum target, WebGLRenderbuffer*);
 
-    OwnPtr<blink::WebGraphicsContext3D> m_context;
-    RefPtr<WebGLContextGroup> m_contextGroup;
-
     // Structure for rendering to a DrawingBuffer, instead of directly
     // to the back-buffer of m_context.
     RefPtr<DrawingBuffer> m_drawingBuffer;
+    RefPtr<WebGLContextGroup> m_contextGroup;
 
     // Dispatches a context lost event once it is determined that one is needed.
     // This is used both for synthetic and real context losses. For real ones, it's

third_party/WebKit/Source/core/html/canvas/WebGLShader.cpp

@@ -42,7 +42,7 @@ WebGLShader::WebGLShader(WebGLRenderingContextBase* ctx, GLenum type)
     , m_source("")
 {
     ScriptWrappable::init(this);
-    setObject(ctx->webGraphicsContext3D()->createShader(type));
+    setObject(ctx->webContext()->createShader(type));
 }
 
 WebGLShader::~WebGLShader()

third_party/WebKit/Source/core/html/canvas/WebGLTexture.cpp

@@ -51,7 +51,7 @@ WebGLTexture::WebGLTexture(WebGLRenderingContextBase* ctx)
     , m_isHalfFloatType(false)
 {
     ScriptWrappable::init(this);
-    setObject(ctx->webGraphicsContext3D()->createTexture());
+    setObject(ctx->webContext()->createTexture());
 }
 
 WebGLTexture::~WebGLTexture()

third_party/WebKit/Source/core/html/canvas/WebGLVertexArrayObjectOES.cpp

@@ -49,7 +49,7 @@ WebGLVertexArrayObjectOES::WebGLVertexArrayObjectOES(WebGLRenderingContextBase*
     case VaoTypeDefault:
         break;
     default:
-        setObject(context()->webGraphicsContext3D()->createVertexArrayOES());
+        setObject(context()->webContext()->createVertexArrayOES());
         break;
     }
 }
@@ -65,7 +65,7 @@ void WebGLVertexArrayObjectOES::deleteObjectImpl(blink::WebGraphicsContext3D* co
     case VaoTypeDefault:
         break;
     default:
-        context()->webGraphicsContext3D()->deleteVertexArrayOES(object);
+        context()->webContext()->deleteVertexArrayOES(object);
         break;
     }
 
@@ -84,7 +84,7 @@ void WebGLVertexArrayObjectOES::setElementArrayBuffer(PassRefPtr<WebGLBuffer> bu
     if (buffer)
         buffer->onAttached();
     if (m_boundElementArrayBuffer)
-        m_boundElementArrayBuffer->onDetached(context()->webGraphicsContext3D());
+        m_boundElementArrayBuffer->onDetached(context()->webContext());
     m_boundElementArrayBuffer = buffer;
 
 }
@@ -99,7 +99,7 @@ void WebGLVertexArrayObjectOES::setVertexAttribState(
     if (buffer)
         buffer->onAttached();
     if (state.bufferBinding)
-        state.bufferBinding->onDetached(context()->webGraphicsContext3D());
+        state.bufferBinding->onDetached(context()->webContext());
 
     state.bufferBinding = buffer;
     state.bytesPerElement = bytesPerElement;
@@ -114,14 +114,14 @@ void WebGLVertexArrayObjectOES::setVertexAttribState(
 void WebGLVertexArrayObjectOES::unbindBuffer(PassRefPtr<WebGLBuffer> buffer)
 {
     if (m_boundElementArrayBuffer == buffer) {
-        m_boundElementArrayBuffer->onDetached(context()->webGraphicsContext3D());
+        m_boundElementArrayBuffer->onDetached(context()->webContext());
         m_boundElementArrayBuffer = nullptr;
     }
 
     for (size_t i = 0; i < m_vertexAttribState.size(); ++i) {
         VertexAttribState& state = m_vertexAttribState[i];
         if (state.bufferBinding == buffer) {
-            buffer->onDetached(context()->webGraphicsContext3D());
+            buffer->onDetached(context()->webContext());
             state.bufferBinding = nullptr;
         }
     }

third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp

@@ -77,9 +77,10 @@ private:
     Platform3DObject m_oldTextureUnitZeroId;
 };
 
-PassRefPtr<DrawingBuffer> DrawingBuffer::create(blink::WebGraphicsContext3D* context, const IntSize& size, PreserveDrawingBuffer preserve, PassRefPtr<ContextEvictionManager> contextEvictionManager)
+PassRefPtr<DrawingBuffer> DrawingBuffer::create(PassOwnPtr<blink::WebGraphicsContext3D> context, const IntSize& size, PreserveDrawingBuffer preserve, PassRefPtr<ContextEvictionManager> contextEvictionManager)
 {
-    Extensions3DUtil extensionsUtil(context);
+    ASSERT(context);
+    Extensions3DUtil extensionsUtil(context.get());
     bool multisampleSupported = extensionsUtil.supportsExtension("GL_CHROMIUM_framebuffer_multisample")
         && extensionsUtil.supportsExtension("GL_OES_rgb8_rgba8");
     if (multisampleSupported) {
@@ -90,12 +91,13 @@ PassRefPtr<DrawingBuffer> DrawingBuffer::create(blink::WebGraphicsContext3D* con
     if (packedDepthStencilSupported)
         extensionsUtil.ensureExtensionEnabled("GL_OES_packed_depth_stencil");
 
-    RefPtr<DrawingBuffer> drawingBuffer = adoptRef(new DrawingBuffer(context, size, multisampleSupported, packedDepthStencilSupported, preserve, contextEvictionManager));
+    RefPtr<DrawingBuffer> drawingBuffer = adoptRef(new DrawingBuffer(context, multisampleSupported, packedDepthStencilSupported, preserve, contextEvictionManager));
+    if (!drawingBuffer->initialize(size))
+        return PassRefPtr<DrawingBuffer>();
     return drawingBuffer.release();
 }
 
-DrawingBuffer::DrawingBuffer(blink::WebGraphicsContext3D* context,
-    const IntSize& size,
+DrawingBuffer::DrawingBuffer(PassOwnPtr<blink::WebGraphicsContext3D> context,
     bool multisampleExtensionSupported,
     bool packedDepthStencilExtensionSupported,
     PreserveDrawingBuffer preserve,
@@ -124,12 +126,12 @@ DrawingBuffer::DrawingBuffer(blink::WebGraphicsContext3D* context,
     , m_colorFormat(0)
     , m_internalRenderbufferFormat(0)
     , m_maxTextureSize(0)
+    , m_sampleCount(0)
     , m_packAlignment(4)
     , m_contextEvictionManager(contextEvictionManager)
 {
     // Used by browser tests to detect the use of a DrawingBuffer.
     TRACE_EVENT_INSTANT0("test_gpu", "DrawingBufferCreation");
-    initialize(size);
 }
 
 DrawingBuffer::~DrawingBuffer()
@@ -156,12 +158,12 @@ void DrawingBuffer::markLayerComposited()
 
 blink::WebGraphicsContext3D* DrawingBuffer::context()
 {
-    return m_context;
+    return m_context.get();
 }
 
 bool DrawingBuffer::prepareMailbox(blink::WebExternalTextureMailbox* outMailbox, blink::WebExternalBitmap* bitmap)
 {
-    if (!m_context || !m_contentsChanged)
+    if (!m_contentsChanged)
         return false;
 
     m_context->makeContextCurrent();
@@ -182,7 +184,7 @@ bool DrawingBuffer::prepareMailbox(blink::WebExternalTextureMailbox* outMailbox,
 
     // We must restore the texture binding since creating new textures,
     // consuming and producing mailboxes changes it.
-    ScopedTextureUnit0BindingRestorer restorer(m_context, m_activeTextureUnit, m_texture2DBinding);
+    ScopedTextureUnit0BindingRestorer restorer(m_context.get(), m_activeTextureUnit, m_texture2DBinding);
 
     // First try to recycle an old buffer.
     RefPtr<MailboxInfo> frontColorBufferMailbox = recycledMailbox();
@@ -245,7 +247,7 @@ void DrawingBuffer::mailboxReleased(const blink::WebExternalTextureMailbox& mail
 
 PassRefPtr<DrawingBuffer::MailboxInfo> DrawingBuffer::recycledMailbox()
 {
-    if (!m_context || m_recycledMailboxes.isEmpty())
+    if (m_recycledMailboxes.isEmpty())
         return PassRefPtr<MailboxInfo>();
 
     RefPtr<MailboxInfo> mailboxInfo = m_recycledMailboxes.last().release();
@@ -275,11 +277,10 @@ PassRefPtr<DrawingBuffer::MailboxInfo> DrawingBuffer::createNewMailbox(unsigned
     return returnMailbox.release();
 }
 
-void DrawingBuffer::initialize(const IntSize& size)
+bool DrawingBuffer::initialize(const IntSize& size)
 {
-    ASSERT(m_context);
     m_attributes = m_context->getContextAttributes();
-    Extensions3DUtil extensionsUtil(m_context);
+    Extensions3DUtil extensionsUtil(m_context.get());
 
     if (m_attributes.alpha) {
         m_internalColorFormat = GL_RGBA;
@@ -312,12 +313,12 @@ void DrawingBuffer::initialize(const IntSize& size)
     else
         m_context->framebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, m_colorBuffer, 0);
     createSecondaryBuffers();
-    reset(size);
+    return reset(size);
 }
 
 bool DrawingBuffer::copyToPlatformTexture(blink::WebGraphicsContext3D* context, Platform3DObject texture, GLenum internalFormat, GLenum destType, GLint level, bool premultiplyAlpha, bool flipY)
 {
-    if (!m_context || !m_context->makeContextCurrent())
+    if (!m_context->makeContextCurrent())
         return false;
     if (m_contentsChanged) {
         if (m_multisampleMode != None) {
@@ -363,9 +364,6 @@ Platform3DObject DrawingBuffer::framebuffer() const
 
 blink::WebLayer* DrawingBuffer::platformLayer()
 {
-    if (!m_context)
-        return 0;
-
     if (!m_layer) {
         m_layer = adoptPtr(blink::Platform::current()->compositorSupport()->createExternalTextureLayer(this));
 
@@ -380,7 +378,7 @@ blink::WebLayer* DrawingBuffer::platformLayer()
 
 void DrawingBuffer::paintCompositedResultsToCanvas(ImageBuffer* imageBuffer)
 {
-    if (!m_context || !m_context->makeContextCurrent() || m_context->getGraphicsResetStatusARB() != GL_NO_ERROR)
+    if (!m_context->makeContextCurrent() || m_context->getGraphicsResetStatusARB() != GL_NO_ERROR)
         return;
 
     if (!imageBuffer)
@@ -421,40 +419,37 @@ void DrawingBuffer::clearPlatformLayer()
     if (m_layer)
         m_layer->clearTexture();
 
-    if (m_context)
-        m_context->flush();
+    m_context->flush();
 }
 
 void DrawingBuffer::releaseResources()
 {
-    if (m_context) {
-        m_context->makeContextCurrent();
+    m_context->makeContextCurrent();
 
-        clearPlatformLayer();
+    clearPlatformLayer();
 
-        for (size_t i = 0; i < m_textureMailboxes.size(); i++)
-            m_context->deleteTexture(m_textureMailboxes[i]->textureId);
+    for (size_t i = 0; i < m_textureMailboxes.size(); i++)
+        m_context->deleteTexture(m_textureMailboxes[i]->textureId);
 
-        if (m_multisampleColorBuffer)
-            m_context->deleteRenderbuffer(m_multisampleColorBuffer);
+    if (m_multisampleColorBuffer)
+        m_context->deleteRenderbuffer(m_multisampleColorBuffer);
 
-        if (m_depthStencilBuffer)
-            m_context->deleteRenderbuffer(m_depthStencilBuffer);
+    if (m_depthStencilBuffer)
+        m_context->deleteRenderbuffer(m_depthStencilBuffer);
 
-        if (m_depthBuffer)
-            m_context->deleteRenderbuffer(m_depthBuffer);
+    if (m_depthBuffer)
+        m_context->deleteRenderbuffer(m_depthBuffer);
 
-        if (m_stencilBuffer)
-            m_context->deleteRenderbuffer(m_stencilBuffer);
+    if (m_stencilBuffer)
+        m_context->deleteRenderbuffer(m_stencilBuffer);
 
-        if (m_multisampleFBO)
-            m_context->deleteFramebuffer(m_multisampleFBO);
+    if (m_multisampleFBO)
+        m_context->deleteFramebuffer(m_multisampleFBO);
 
-        if (m_fbo)
-            m_context->deleteFramebuffer(m_fbo);
+    if (m_fbo)
+        m_context->deleteFramebuffer(m_fbo);
 
-        m_context = 0;
-    }
+    m_context.clear();
 
     setSize(IntSize());
 
@@ -479,9 +474,6 @@ void DrawingBuffer::releaseResources()
 
 unsigned DrawingBuffer::createColorTexture(const IntSize& size)
 {
-    if (!m_context)
-        return 0;
-
     unsigned offscreenColorTexture = m_context->createTexture();
     if (!offscreenColorTexture)
         return 0;
@@ -598,9 +590,6 @@ void DrawingBuffer::resizeDepthStencil(const IntSize& size)
 
 void DrawingBuffer::clearFramebuffers(GLbitfield clearMask)
 {
-    if (!m_context)
-        return;
-
     // We will clear the multisample FBO, but we also need to clear the non-multisampled buffer.
     if (m_multisampleFBO) {
         m_context->bindFramebuffer(GL_FRAMEBUFFER, m_fbo);
@@ -668,11 +657,9 @@ IntSize DrawingBuffer::adjustSizeWithContextEviction(const IntSize& size, bool&
     return adjustedSize;
 }
 
-void DrawingBuffer::reset(const IntSize& newSize)
+bool DrawingBuffer::reset(const IntSize& newSize)
 {
-    if (!m_context)
-        return;
-
+    ASSERT(!newSize.isEmpty());
     IntSize adjustedSize;
     bool evictContext = false;
     bool isNewContext = m_size.isEmpty();
@@ -682,7 +669,7 @@ void DrawingBuffer::reset(const IntSize& newSize)
         adjustedSize = adjustSize(newSize);
 
     if (adjustedSize.isEmpty())
-        return;
+        return false;
 
     if (evictContext)
         m_contextEvictionManager->forciblyLoseOldestContext("WARNING: WebGL contexts have exceeded the maximum allowed backbuffer area. Oldest context will be lost.");
@@ -700,7 +687,7 @@ void DrawingBuffer::reset(const IntSize& newSize)
         setSize(adjustedSize);
 
         if (adjustedSize.isEmpty())
-            return;
+            return false;
     }
 
     m_context->disable(GL_SCISSOR_TEST);
@@ -720,13 +707,11 @@ void DrawingBuffer::reset(const IntSize& newSize)
     }
 
     clearFramebuffers(clearMask);
+    return true;
 }
 
 void DrawingBuffer::commit(long x, long y, long width, long height)
 {
-    if (!m_context)
-        return;
-
     if (width < 0)
         width = m_size.width();
     if (height < 0)
@@ -754,7 +739,7 @@ void DrawingBuffer::commit(long x, long y, long width, long height)
 
 void DrawingBuffer::restoreFramebufferBinding()
 {
-    if (!m_context || !m_framebufferBinding)
+    if (!m_framebufferBinding)
         return;
 
     m_context->bindFramebuffer(GL_FRAMEBUFFER, m_framebufferBinding);
@@ -767,9 +752,6 @@ bool DrawingBuffer::multisample() const
 
 void DrawingBuffer::bind()
 {
-    if (!m_context)
-        return;
-
     m_context->bindFramebuffer(GL_FRAMEBUFFER, m_multisampleFBO ? m_multisampleFBO : m_fbo);
 }
 

third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.h

@@ -79,24 +79,19 @@ public:
         Discard
     };
 
-    static PassRefPtr<DrawingBuffer> create(blink::WebGraphicsContext3D*, const IntSize&, PreserveDrawingBuffer, PassRefPtr<ContextEvictionManager>);
+    static PassRefPtr<DrawingBuffer> create(PassOwnPtr<blink::WebGraphicsContext3D>, const IntSize&, PreserveDrawingBuffer, PassRefPtr<ContextEvictionManager>);
 
     virtual ~DrawingBuffer();
 
-    // Clear all resources from this object, as well as context. Called when context is destroyed
-    // to prevent invalid accesses to the resources.
-    void releaseResources();
-
     // Issues a glClear() on all framebuffers associated with this DrawingBuffer. The caller is responsible for
     // making the context current and setting the clear values and masks. Modifies the framebuffer binding.
     void clearFramebuffers(GLbitfield clearMask);
 
     // Given the desired buffer size, provides the largest dimensions that will fit in the pixel budget.
     IntSize adjustSize(const IntSize&);
-    void reset(const IntSize&);
+    bool reset(const IntSize&);
     void bind();
     IntSize size() const { return m_size; }
-    bool isZeroSized() const { return m_size.isEmpty(); }
 
     // Copies the multisample color buffer to the normal color buffer and leaves m_fbo bound.
     void commit(long x = 0, long y = 0, long width = -1, long height = -1);
@@ -143,10 +138,11 @@ public:
     PassRefPtr<Uint8ClampedArray> paintRenderingResultsToImageData(int&, int&);
 
 private:
-    DrawingBuffer(blink::WebGraphicsContext3D*, const IntSize&, bool multisampleExtensionSupported,
+    DrawingBuffer(PassOwnPtr<blink::WebGraphicsContext3D>, bool multisampleExtensionSupported,
                   bool packedDepthStencilExtensionSupported, PreserveDrawingBuffer, PassRefPtr<ContextEvictionManager>);
 
-    void initialize(const IntSize&);
+    bool initialize(const IntSize&);
+    void releaseResources();
 
     unsigned createColorTexture(const IntSize& size = IntSize());
     // Create the depth/stencil and multisample buffers, if needed.
@@ -198,7 +194,7 @@ private:
     Platform3DObject m_framebufferBinding;
     GLenum m_activeTextureUnit;
 
-    blink::WebGraphicsContext3D* m_context;
+    OwnPtr<blink::WebGraphicsContext3D> m_context;
     IntSize m_size;
     bool m_multisampleExtensionSupported;
     bool m_packedDepthStencilExtensionSupported;

third_party/WebKit/Source/web/tests/DrawingBufferTest.cpp

@@ -112,16 +112,17 @@ protected:
     virtual void SetUp()
     {
         RefPtr<FakeContextEvictionManager> contextEvictionManager = adoptRef(new FakeContextEvictionManager());
-        m_context = adoptPtr(new WebGraphicsContext3DForTests);
-        m_drawingBuffer = DrawingBuffer::create(m_context.get(), IntSize(initialWidth, initialHeight), DrawingBuffer::Preserve, contextEvictionManager.release());
+        OwnPtr<WebGraphicsContext3DForTests> context = adoptPtr(new WebGraphicsContext3DForTests);
+        m_context = context.get();
+        m_drawingBuffer = DrawingBuffer::create(context.release(), IntSize(initialWidth, initialHeight), DrawingBuffer::Preserve, contextEvictionManager.release());
     }
 
     WebGraphicsContext3DForTests* webContext()
     {
-        return m_context.get();
+        return m_context;
     }
 
-    OwnPtr<WebGraphicsContext3DForTests> m_context;
+    WebGraphicsContext3DForTests* m_context;
     RefPtr<DrawingBuffer> m_drawingBuffer;
 };
 
@@ -141,16 +142,6 @@ TEST_F(DrawingBufferTest, testPaintRenderingResultsToCanvas)
     EXPECT_FALSE(imageBuffer->bitmap().isNull());
 }
 
-TEST_F(DrawingBufferTest, verifyNoNewBuffersAfterContextLostWithMailboxes)
-{
-    // Tell the buffer its contents changed and context was lost.
-    m_drawingBuffer->markContentsChanged();
-    m_drawingBuffer->releaseResources();
-
-    blink::WebExternalTextureMailbox mailbox;
-    EXPECT_FALSE(m_drawingBuffer->prepareMailbox(&mailbox, 0));
-}
-
 TEST_F(DrawingBufferTest, verifyResizingProperlyAffectsMailboxes)
 {
     blink::WebExternalTextureMailbox mailbox;