Add platform APIs for the unprefixed EME APIs.

public/platform/Platform.h

Index: public/platform/Platform.h
diff --git a/public/platform/Platform.h b/public/platform/Platform.h
index acff9862dc1663b4f3cc6a0b73606bc332a52457..853116013f5e8a81bf27d4538773d980c6ab9dca 100644
--- a/public/platform/Platform.h
+++ b/public/platform/Platform.h
@@ -51,6 +51,7 @@ namespace WebKit {
 
 class WebAudioBus;
 class WebBlobRegistry;
+class WebContentDecryptionModule;
 class WebClipboard;
 class WebCompositorSupport;
 class WebCookieJar;
@@ -129,6 +130,13 @@ public:
     // May return null.
     virtual WebSpeechSynthesizer* createSpeechSynthesizer(WebSpeechSynthesizerClient*) { return 0; }
 
+
+    // Media --------------------------------------------------------------
+
+    // May return null.
+    virtual WebContentDecryptionModule* createContentDecryptionModule(const WebString& keySystem) { return 0; }
+
+
     // Audio --------------------------------------------------------------
 
     virtual double audioHardwareSampleRate() { return 0; }