Rename blink::Prerender::referrer() to getReferrer().

The rename is needed to avoid a naming collision after changing from
Blink to Chromium naming style.  Right now we have a |Referrer| type and
a |referrer| accessor method (differing by case of the first character);
after a naive rename by the rewrite_to_chrome_style tool we would end up
with |Referrer| being the name of both the type and the accessor method
(with both living in the same namespace).

Prepending a "get" prefix to the name of the accessor method is the
workaround that fits into the guidance on the recommended
post-Blink-to-Chromium-rename style suggested by esprehn@ in
https://crbug.com/582312#c17:
- Getters favor not using "Get", ex. FirstChild()
- Unless the type name conflicts, in which case you can either rename
  the type if it's easy and makes sense, or add "Get", ex. GetContext().

BUG=582312

Review-Url: https://codereview.chromium.org/2308063002
Cr-Commit-Position: refs/heads/master@{#417044}

third_party/WebKit/Source/platform/Prerender.h

@@ -69,7 +69,7 @@ public:
 
     const KURL& url() const { return m_url; }
     unsigned relTypes() const { return m_relTypes; }
-    const String& referrer() const { return m_referrer.referrer; }
+    const String& getReferrer() const { return m_referrer.referrer; }
     ReferrerPolicy getReferrerPolicy() const { return m_referrer.referrerPolicy; }
 
     void setExtraData(PassRefPtr<ExtraData> extraData) { m_extraData = extraData; }

third_party/WebKit/Source/platform/exported/WebPrerender.cpp

@@ -95,7 +95,7 @@ unsigned WebPrerender::relTypes() const
 
 WebString WebPrerender::referrer() const
 {
-    return m_private->referrer();
+    return m_private->getReferrer();
 }
 
 WebReferrerPolicy WebPrerender::referrerPolicy() const