Convert string16 to base::string16 in content.

content/common/mac/attributed_string_coder.mm

Index: content/common/mac/attributed_string_coder.mm
diff --git a/content/common/mac/attributed_string_coder.mm b/content/common/mac/attributed_string_coder.mm
index ba6eca535c19cf956acbc42792d6fdf89e29bf5e..f14103bde0f587e2dfed3258e586ef53def52171 100644
--- a/content/common/mac/attributed_string_coder.mm
+++ b/content/common/mac/attributed_string_coder.mm
@@ -65,7 +65,7 @@ NSAttributedString* AttributedStringCoder::Decode(
 
 // Data Types //////////////////////////////////////////////////////////////////
 
-AttributedStringCoder::EncodedString::EncodedString(string16 string)
+AttributedStringCoder::EncodedString::EncodedString(base::string16 string)
     : string_(string) {
 }
 
@@ -129,7 +129,7 @@ bool ParamTraits<AttributedStringCoder::EncodedString>::Read(
     const Message* m, PickleIterator* iter, param_type* p) {
   bool success = true;
 
-  string16 result;
+  base::string16 result;
   success &= ReadParam(m, iter, &result);
   *p = AttributedStringCoder::EncodedString(result);