Add RTC_ prefix to contructormagic macros.

We must remove dependency on Chromium, i.e. we can't use Chromium's base/logging.h. That means we need to define these macros in WebRTC also when doing Chromium builds. And this causes redefinition.

* DISALLOW_ASSIGN -> RTC_DISALLOW_ASSIGN
* DISALLOW_COPY_AND_ASSIGN -> RTC_DISALLOW_COPY_AND_ASSIGN
* DISALLOW_IMPLICIT_CONSTRUCTORS -> RTC_DISALLOW_IMPLICIT_CONSTRUCTORS

Related CL: https://codereview.webrtc.org/1335923002/

BUG=chromium:468375
NOTRY=true

Review URL: https://codereview.webrtc.org/1345433002

Cr-Commit-Position: refs/heads/master@{#9953}
diff --git a/talk/app/webrtc/jsepsessiondescription.h b/talk/app/webrtc/jsepsessiondescription.h
index 53f4e06..756352c 100644
--- a/talk/app/webrtc/jsepsessiondescription.h
+++ b/talk/app/webrtc/jsepsessiondescription.h
@@ -98,7 +98,7 @@
   bool GetMediasectionIndex(const IceCandidateInterface* candidate,
                             size_t* index);
 
-  DISALLOW_COPY_AND_ASSIGN(JsepSessionDescription);
+  RTC_DISALLOW_COPY_AND_ASSIGN(JsepSessionDescription);
 };
 
 }  // namespace webrtc