Improve RAII of StyleResolverState.

Source/core/css/resolver/StyleBuilderCustom.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 2004-2005 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2006, 2007 Nicholas Shanks (webkit@nickshanks.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  * Copyright (C) 2007, 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (c) 2011, Code Aurora Forum. All rights reserved.
@@ skipping 559 matching lines @@
         state.style()->setVerticalAlign(*primitiveValue);
         return;
     }
 
     state.style()->setVerticalAlignLength(primitiveValue->convertToLength<FixedConversion | PercentConversion>(state.cssToLengthConversionData()));
 }
 
 static void resetEffectiveZoom(StyleResolverState& state)
 {
     // Reset the zoom in effect. This allows the setZoom method to accurately compute a new zoom in effect.
-    state.setEffectiveZoom(state.parentStyle() ? state.parentStyle()->effectiveZoom() : RenderStyle::initialZoom());
+    state.setEffectiveZoom(state.parentStyle()->effectiveZoom());
 }
 
 void StyleBuilderFunctions::applyInitialCSSPropertyZoom(StyleResolverState& state)
 {
     resetEffectiveZoom(state);
     state.setZoom(RenderStyle::initialZoom());
 }
 
 void StyleBuilderFunctions::applyInheritCSSPropertyZoom(StyleResolverState& state)
 {
@@ skipping 330 matching lines @@
         return;
     case CSSValueSuper:
         svgStyle.setBaselineShift(BS_SUPER);
         return;
     default:
         ASSERT_NOT_REACHED();
     }
 }
 
 } // namespace blink