Make calls to AtomicString(const String&) explicit in dom/

Source/core/dom/Attr.cpp

Index: Source/core/dom/Attr.cpp
diff --git a/Source/core/dom/Attr.cpp b/Source/core/dom/Attr.cpp
index b67b2818f656b511133a9961d0c73f0178ec4041..f87cb6c33d2d173f129d77016be602137c94b5cb 100644
--- a/Source/core/dom/Attr.cpp
+++ b/Source/core/dom/Attr.cpp
@@ -143,7 +143,7 @@ void Attr::setValue(const AtomicString& value, ExceptionState&)
 
 void Attr::setNodeValue(const String& v)

[eseidel, 2013/12/15 16:51:26]

Does this eventually change to AtomicString too?

[Inactive, 2013/12/16 14:26:27]

The reason I did not update setNodeValue() to take an AtomicString is that this
is a virtual method and not all class implementing it expect an AtomicString.
For e.g. CharacterData::setNodeValue() expects a String.

[eseidel, 2013/12/30 17:19:27]

But why are values atomic in the first place?  What are typical node values?

[Inactive, 2013/12/30 19:53:34]

Node values are not atomic, they are Strings and I did not change that.
setNodeValue() virtual method is implemented by both Attr and CharacterData.
Using AtomicString for the CharacterData text does not seem to make much sense.
However, Attr uses AtomicString internally to store its value (The value of an
Element's attribute). 

I assume there is a lot of duplication among Element attributes values on a Web
page. Therefore, using AtomicString for them seems to make sense to save memory.
I think calling AtomicString() explicitly here is the right thing to do as I
don't think we want to move CharacterData's data to AtomicString type.

 {
-    setValue(v, IGNORE_EXCEPTION);
+    setValue(AtomicString(v), IGNORE_EXCEPTION);
 }
 
 PassRefPtr<Node> Attr::cloneNode(bool /*deep*/)