Replace scoped_ptr with unique_ptr everywhere

But keep #including scoped_ptr.h in .h files, so as not to break
WebRTC users who expect those .h files to give them rtc::scoped_ptr.

BUG=webrtc:5520

Review-Url: https://codereview.webrtc.org/1937693002
Cr-Commit-Position: refs/heads/master@{#12581}

webrtc/sdk/objc/Framework/Classes/RTCOpenGLVideoRenderer.mm

@@ -16,10 +16,10 @@
 #import <OpenGL/gl3.h>
 #endif
 #include <string.h>
+#include <memory>
 
 #import "WebRTC/RTCVideoFrame.h"
 
-#include "webrtc/base/scoped_ptr.h"
 
 // TODO(tkchin): check and log openGL errors. Methods here return BOOLs in
 // anticipation of that happening in the future.
@@ -162,7 +162,7 @@ static const GLsizei kNumTextures = 3 * kNumTextureSets;
   GLint _vSampler;
   // Used to create a non-padded plane for GPU upload when we receive padded
   // frames.
-  rtc::scoped_ptr<uint8_t[]> _planeBuffer;
+  std::unique_ptr<uint8_t[]> _planeBuffer;
 }
 
 @synthesize lastDrawnFrame = _lastDrawnFrame;