Removed file RTCCameraVideoCapturer.mm that isn't needed

Also added post commit review changes.

BUG=webrtc:7898

Review-Url: https://codereview.webrtc.org/2988783002
Cr-Commit-Position: refs/heads/master@{#19145}

webrtc/sdk/objc/Framework/Classes/Video/AVCaptureSession+DevicePosition.h

@@ -13,7 +13,7 @@
 
 NS_ASSUME_NONNULL_BEGIN
 
-@interface AVCaptureSession (Device)
+@interface AVCaptureSession (DevicePosition)
 
 // Check the image's EXIF for the camera the image came from.
 + (AVCaptureDevicePosition)devicePositionForSampleBuffer:(CMSampleBufferRef)sampleBuffer;

webrtc/sdk/objc/Framework/Classes/Video/AVCaptureSession+DevicePosition.mm

@@ -8,7 +8,7 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#import "AVCaptureSession+Device.h"
+#import "AVCaptureSession+DevicePosition.h"
 
 BOOL CFStringContainsString(CFStringRef theString, CFStringRef stringToFind) {
   return CFStringFindWithOptions(theString,
@@ -18,7 +18,7 @@ BOOL CFStringContainsString(CFStringRef theString, CFStringRef stringToFind) {
                                  nil);
 }
 
-@implementation AVCaptureSession (Device)
+@implementation AVCaptureSession (DevicePosition)
 
 + (AVCaptureDevicePosition)devicePositionForSampleBuffer:(CMSampleBufferRef)sampleBuffer {
   // Check the image's EXIF for the camera the image came from.

webrtc/sdk/objc/Framework/Classes/Video/RTCAVFoundationVideoCapturerInternal.mm

@@ -16,7 +16,7 @@
 #import "WebRTC/UIDevice+RTCDevice.h"
 #endif
 
-#import "AVCaptureSession+Device.h"
+#import "AVCaptureSession+DevicePosition.h"
 #import "RTCDispatcher+Private.h"
 #import "WebRTC/RTCLogging.h"
 
@@ -218,7 +218,7 @@
 #if TARGET_OS_IPHONE
   // Default to portrait orientation on iPhone.
   webrtc::VideoRotation rotation = webrtc::kVideoRotation_90;
-  BOOL usingFrontCamera;
+  BOOL usingFrontCamera = NO;
   // Check the image's EXIF for the camera the image came from as the image could have been
   // delayed as we set alwaysDiscardsLateVideoFrames to NO.
   AVCaptureDevicePosition cameraPosition =