Remove createContentDecryptionModule() from platform.h

This method is no longer being called, and can be removed.

BUG=250049
TEST=encrypted media layout and browser tests pass

Review URL: https://codereview.chromium.org/197333006

git-svn-id: svn://svn.chromium.org/blink/trunk@169999 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/public/platform/Platform.h

@@ -141,12 +141,6 @@ public:
     virtual WebSpeechSynthesizer* createSpeechSynthesizer(WebSpeechSynthesizerClient*) { return 0; }
 
 
-    // Media --------------------------------------------------------------
-
-    // May return null.
-    virtual WebContentDecryptionModule* createContentDecryptionModule(const WebString& keySystem) { return 0; }
-
-
     // Audio --------------------------------------------------------------
 
     virtual double audioHardwareSampleRate() { return 0; }