Avoid re-parsing of string in fillText and measureText in Canvas

Source/platform/text/TextRun.cpp

 /*
  * Copyright (C) 2011 Apple Inc. 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.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 18 matching lines @@
 namespace blink {
 
 struct ExpectedTextRunSize {
     const void* pointer;
     int integers[2];
     float float1;
     float float2;
     float float3;
     uint32_t bitfields : 10;
     unsigned anUnsigned;
+    bool b;
     RefPtr<TextRun::RenderingContext> renderingContext;
 };
 
 COMPILE_ASSERT(sizeof(TextRun) == sizeof(ExpectedTextRunSize), TextRun_is_not_of_expected_size);
 
 void TextRun::setText(const String& string)
 {
     m_len = string.length();
     if (!m_len) {
         m_data.characters8 = 0;
         m_is8Bit = true;
         return;
     }
     m_is8Bit = string.is8Bit();
     if (m_is8Bit)
         m_data.characters8 = string.characters8();
     else
         m_data.characters16 = string.characters16();
 }
 
 }