Prevent crash when calling text-related methods on a 2D canvas in a frame-less document.

Source/core/html/canvas/CanvasRenderingContext2D.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2007 Alp Toker <alp@atoker.com>
  * Copyright (C) 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2008 Dirk Schulze <krit@webkit.org>
  * Copyright (C) 2010 Torch Mobile (Beijing) Co. Ltd. All rights reserved.
  * Copyright (C) 2012, 2013 Intel Corporation. All rights reserved.
  * Copyright (C) 2013 Adobe Systems Incorporated. All rights reserved.
  *
@@ skipping 2063 matching lines @@
 
         serializedFont.append(' ');
         serializedFont.append(family);
     }
 
     return serializedFont.toString();
 }
 
 void CanvasRenderingContext2D::setFont(const String& newFont)
 {
+    // The style resolution required for rendering text is not available in frame-less documents.
+    if (!canvas()->document().frame())
+        return;
+
     MutableStylePropertyMap::iterator i = m_fetchedFonts.find(newFont);
     RefPtr<MutableStylePropertySet> parsedStyle = i != m_fetchedFonts.end() ? i->value : nullptr;
 
     if (!parsedStyle) {
         parsedStyle = MutableStylePropertySet::create();
         CSSParserMode mode = m_usesCSSCompatibilityParseMode ? HTMLQuirksMode : HTMLStandardMode;
         BisonCSSParser::parseValue(parsedStyle.get(), CSSPropertyFont, newFont, true, mode, 0);
         m_fetchedFonts.add(newFont, parsedStyle);
     }
     if (parsedStyle->isEmpty())
@@ skipping 98 matching lines @@
     drawTextInternal(text, x, y, false);
 }
 
 void CanvasRenderingContext2D::strokeText(const String& text, float x, float y, float maxWidth)
 {
     drawTextInternal(text, x, y, false, maxWidth, true);
 }
 
 PassRefPtr<TextMetrics> CanvasRenderingContext2D::measureText(const String& text)
 {
+    RefPtr<TextMetrics> metrics = TextMetrics::create();
+
+    // The style resolution required for rendering text is not available in frame-less documents.
+    if (!canvas()->document().frame())
+        return metrics.release();
+
     FontCachePurgePreventer fontCachePurgePreventer;
-    RefPtr<TextMetrics> metrics = TextMetrics::create();
     canvas()->document().updateStyleIfNeeded();
     metrics->setWidth(accessFont().width(TextRun(text)));
     return metrics.release();
 }
 
 static void replaceCharacterInString(String& text, WTF::CharacterMatchFunctionPtr matchFunction, const String& replacement)
 {
     const size_t replacementLength = replacement.length();
     size_t index = 0;
     while ((index = text.find(matchFunction, index)) != kNotFound) {
         text.replace(index, 1, replacement);
         index += replacementLength;
     }
 }
 
 void CanvasRenderingContext2D::drawTextInternal(const String& text, float x, float y, bool fill, float maxWidth, bool useMaxWidth)
 {
+    // The style resolution required for rendering text is not available in frame-less documents.
+    if (!canvas()->document().frame())
+        return;
+
     // accessFont needs the style to be up to date, but updating style can cause script to run,
     // (e.g. due to autofocus) which can free the GraphicsContext, so update style before grabbing
     // the GraphicsContext.
     canvas()->document().updateStyleIfNeeded();
 
     GraphicsContext* c = drawingContext();
     if (!c)
         return;
     if (!state().m_invertibleCTM)
         return;
@@ skipping 238 matching lines @@
     const int focusRingWidth = 5;
     const int focusRingOutline = 0;
     c->drawFocusRing(path, focusRingWidth, focusRingOutline, focusRingColor);
 
     c->restore();
 
     didDraw(dirtyRect);
 }
 
 } // namespace WebCore