Cleanup namespace usage in public/web/Web[A-M]*.h.

public/web/WebMIDIClientMock.h

Index: public/web/WebMIDIClientMock.h
diff --git a/public/web/WebMIDIClientMock.h b/public/web/WebMIDIClientMock.h
index 34b62a8d6dd56e2106c34441ca28f8aca9769c5d..4a775c266b7c5994271cbcaddde1153eda598101 100644
--- a/public/web/WebMIDIClientMock.h
+++ b/public/web/WebMIDIClientMock.h
@@ -36,10 +36,8 @@
 #include "WebMIDIClient.h"
 
 namespace blink {
-class MIDIClientMock;
-}
 
-namespace blink {
+class MIDIClientMock;
 
 class WebMIDIClientMock : public WebMIDIClient {
 public:
@@ -56,7 +54,7 @@ public:
 private:
     BLINK_EXPORT void reset();
 
-    WebPrivateOwnPtr<blink::MIDIClientMock> m_clientMock;
+    WebPrivateOwnPtr<MIDIClientMock> m_clientMock;
 };
 
 } // namespace blink