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/webrtc/base/fileutils.h b/webrtc/base/fileutils.h
index 1533fb5..8d085ef 100644
--- a/webrtc/base/fileutils.h
+++ b/webrtc/base/fileutils.h
@@ -407,7 +407,7 @@
   static FilesystemInterface* default_filesystem_;
 
   static FilesystemInterface *EnsureDefaultFilesystem();
-  DISALLOW_IMPLICIT_CONSTRUCTORS(Filesystem);
+  RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(Filesystem);
 };
 
 class FilesystemScope{
@@ -420,7 +420,7 @@
   }
  private:
   FilesystemInterface* old_fs_;
-  DISALLOW_IMPLICIT_CONSTRUCTORS(FilesystemScope);
+  RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(FilesystemScope);
 };
 
 // Generates a unique filename based on the input path.  If no path component