Add canvas context type histogram

Source/core/html/HTMLCanvasElement.cpp

 /*
  * Copyright (C) 2004, 2006, 2007 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alp Toker <alp@atoker.com>
  * Copyright (C) 2010 Torch Mobile (Beijing) Co. Ltd. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
@@ skipping 21 matching lines @@
 #include "HTMLNames.h"
 #include "bindings/v8/ScriptController.h"
 #include "core/dom/Document.h"
 #include "core/dom/ExceptionCode.h"
 #include "core/html/ImageData.h"
 #include "core/html/canvas/Canvas2DContextAttributes.h"
 #include "core/html/canvas/CanvasRenderingContext2D.h"
 #include "core/page/Frame.h"
 #include "RuntimeEnabledFeatures.h"
 #include "core/page/Settings.h"
+#include "core/platform/HistogramSupport.h"
 #include "core/platform/MIMETypeRegistry.h"
 #include "core/platform/graphics/GraphicsContextStateSaver.h"
 #include "core/platform/graphics/ImageBuffer.h"
 #include "core/rendering/RenderHTMLCanvas.h"
 
 #include "core/html/canvas/WebGLContextAttributes.h"
 #include "core/html/canvas/WebGLRenderingContext.h"
 
 #include "public/platform/Platform.h"
 
@@ skipping 93 matching lines @@
 {
     setAttribute(widthAttr, String::number(value));
 }
 
 CanvasRenderingContext* HTMLCanvasElement::getContext(const String& type, CanvasContextAttributes* attrs)
 {
     // A Canvas can either be "2D" or "webgl" but never both. If you request a 2D canvas and the existing
     // context is already 2D, just return that. If the existing context is WebGL, then destroy it
     // before creating a new 2D context. Vice versa when requesting a WebGL canvas. Requesting a
     // context with any other type string will destroy any existing context.
+    enum ContextType {
+        Context2d,
+        ContextWebkit3d,
+        ContextExperimentalWebgl,
+        ContextWebgl,
+        ContextTypeCount,
+    };

[Mark P, 2013/08/02 15:40:55]

Please add a note that new elements should only be added at the end and that
existing elements should not be reordered.

[Sami, 2013/08/02 16:05:25]

Done.

 
     // FIXME - The code depends on the context not going away once created, to prevent JS from
     // seeing a dangling pointer. So for now we will disallow the context from being changed
     // once it is created.
     if (type == "2d") {
         if (m_context && !m_context->is2d())
             return 0;
         if (!m_context) {
+            HistogramSupport::histogramEnumeration("Canvas.ContextType", Context2d, ContextTypeCount);
             m_context = CanvasRenderingContext2D::create(this, RuntimeEnabledFeatures::experimentalCanvasFeaturesEnabled() ? static_cast<Canvas2DContextAttributes*>(attrs) : 0, document()->inQuirksMode());
             if (m_context)
                 scheduleLayerUpdate();
         }
         return m_context.get();
     }
 
     Settings* settings = document()->settings();
     if (settings && settings->webGLEnabled()) {
-
         // Accept the legacy "webkit-3d" name as well as the provisional "experimental-webgl" name.
-        bool is3dContext = (type == "webkit-3d") || (type == "experimental-webgl");
-
         // Now that WebGL is ratified, we will also accept "webgl" as the context name in Chrome.
-        is3dContext |= (type == "webgl");
+        ContextType contextType;
+        bool is3dContext = true;
+        if (type == "webkit-3d")
+            contextType = ContextWebkit3d;
+        else if (type == "experimental-webgl")
+            contextType = ContextExperimentalWebgl;
+        else if (type == "webgl")
+            contextType = ContextWebgl;
+        else
+            is3dContext = false;
 
         if (is3dContext) {
             if (m_context && !m_context->is3d())
                 return 0;
             if (!m_context) {
+                HistogramSupport::histogramEnumeration("Canvas.ContextType", contextType, ContextTypeCount);
                 m_context = WebGLRenderingContext::create(this, static_cast<WebGLContextAttributes*>(attrs));
                 if (m_context)
                     scheduleLayerUpdate();
             }
             return m_context.get();
         }
     }
     return 0;
 }
 
@@ skipping 374 matching lines @@
     FloatSize unscaledSize = size();
     FloatSize deviceSize = convertLogicalToDevice(unscaledSize);
     IntSize size(deviceSize.width(), deviceSize.height());
     AffineTransform transform;
     if (size.width() && size.height())
         transform.scaleNonUniform(size.width() / unscaledSize.width(), size.height() / unscaledSize.height());
     return m_imageBuffer->baseTransform() * transform;
 }
 
 }