[bindings] Break V8Binding::toDouble into fast inline and slower non-inline code paths.

Source/bindings/core/v8/V8Binding.h

 /*
 * Copyright (C) 2009 Google Inc. All rights reserved.
 * Copyright (C) 2012 Ericsson AB. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
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 // Convert a value to a single precision float, throwing on non-finite values.
 float toRestrictedFloat(v8::Handle<v8::Value>, ExceptionState&);
 
 // Convert a value to a single precision float assuming the conversion cannot fail.
 inline float toFloat(v8::Local<v8::Value> value)
 {
     return static_cast<float>(value->NumberValue());
 }
 
 // Convert a value to a double precision float, which might fail.
-double toDouble(v8::Handle<v8::Value>, ExceptionState&);
+double toDoubleSlow(v8::Handle<v8::Value>, ExceptionState&);
+
+inline double toDouble(v8::Handle<v8::Value> value, ExceptionState& exceptionState)
+{
+    if (value->IsNumber())
+        return value->NumberValue();
+    return toDoubleSlow(value, exceptionState);
+}
 
 // Convert a value to a double precision float, throwing on non-finite values.
 double toRestrictedDouble(v8::Handle<v8::Value>, ExceptionState&);
 
 // Converts a value to a String, throwing if any code unit is outside 0-255.
 String toByteString(v8::Handle<v8::Value>, ExceptionState&);
 
 // Converts a value to a String, replacing unmatched UTF-16 surrogates with replacement characters.
 String toUSVString(v8::Handle<v8::Value>, ExceptionState&);
 
@@ skipping 497 matching lines @@
 
 private:
     v8::TryCatch& m_block;
 };
 
 typedef void (*InstallTemplateFunction)(v8::Local<v8::FunctionTemplate>, v8::Isolate*);
 
 } // namespace blink
 
 #endif // V8Binding_h