Keep TextMetrics on the Oilpan heap always.

Source/modules/canvas2d/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 1875 matching lines @@
 void CanvasRenderingContext2D::strokeText(const String& text, float x, float y)
 {
     drawTextInternal(text, x, y, CanvasRenderingContext2DState::StrokePaintType);
 }
 
 void CanvasRenderingContext2D::strokeText(const String& text, float x, float y, float maxWidth)
 {
     drawTextInternal(text, x, y, CanvasRenderingContext2DState::StrokePaintType, &maxWidth);
 }
 
-PassRefPtrWillBeRawPtr<TextMetrics> CanvasRenderingContext2D::measureText(const String& text)
+TextMetrics* CanvasRenderingContext2D::measureText(const String& text)
 {
-    RefPtrWillBeRawPtr<TextMetrics> metrics = TextMetrics::create();
+    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();
+        return metrics;
 
     canvas()->document().updateLayoutTreeForNodeIfNeeded(canvas());
     const Font& font = accessFont();
 
     TextDirection direction;
     if (state().direction() == CanvasRenderingContext2DState::DirectionInherit)
         direction = determineDirectionality(text);
     else
         direction = toTextDirection(state().direction(), canvas());
     TextRun textRun(text, 0, 0, TextRun::AllowTrailingExpansion | TextRun::ForbidLeadingExpansion, direction, false);
@@ skipping 17 matching lines @@
     metrics->setActualBoundingBoxDescent(textBounds.maxY() + baselineY);
 
     // Note : top/bottom and ascend/descend are currently the same, so there's no difference
     //        between the EM box's top and bottom and the font's ascend and descend
     metrics->setEmHeightAscent(0);
     metrics->setEmHeightDescent(0);
 
     metrics->setHangingBaseline(-0.8f * ascent + baselineY);
     metrics->setAlphabeticBaseline(baselineY);
     metrics->setIdeographicBaseline(descent + baselineY);
-    return metrics.release();
+    return metrics;
 }
 
 void CanvasRenderingContext2D::drawTextInternal(const String& text, float x, float y, CanvasRenderingContext2DState::PaintType paintType, float* maxWidth)
 {
     // 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 canvas (set size to 0, for example), so update
@@ skipping 369 matching lines @@
         if (imageType == CanvasRenderingContext2DState::NonOpaqueImage)
             return;
         if (alpha < 0xFF)
             return;
     }
 
     canvas()->buffer()->willOverwriteCanvas();
 }
 
 } // namespace blink