Pass-by-reference instead of value to initWithNativeEncodedImage

Previously, the use of pass-by-value caused an issue in
ObjCVideoDecoder::Decode, where the EncodedImage was being copied upon
calling initWithNativeEncodedImage, which then created an NSData using
the copy's pointer; then the copy was destroyed, invalidating that
pointer.

Bug: webrtc:9378
Change-Id: Iac28b890c9902108ffc5ec54a607a99034159153
Reviewed-on: https://webrtc-review.googlesource.com/c/121922
Reviewed-by: Kári Helgason <kthelgason@webrtc.org>
Reviewed-by: Niels Moller <nisse@webrtc.org>
Commit-Queue: Rasmus Brandt <brandtr@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#26598}

sdk/objc/api/peerconnection/RTCEncodedImage+Private.h

@@ -17,7 +17,7 @@ NS_ASSUME_NONNULL_BEGIN
 /* Interfaces for converting to/from internal C++ formats. */
 @interface RTCEncodedImage (Private)
 
-- (instancetype)initWithNativeEncodedImage:(webrtc::EncodedImage)encodedImage;
+- (instancetype)initWithNativeEncodedImage:(const webrtc::EncodedImage &)encodedImage;
 - (webrtc::EncodedImage)nativeEncodedImage;
 
 @end

sdk/objc/api/peerconnection/RTCEncodedImage+Private.mm

@@ -14,10 +14,10 @@
 
 @implementation RTCEncodedImage (Private)
 
-- (instancetype)initWithNativeEncodedImage:(webrtc::EncodedImage)encodedImage {
+- (instancetype)initWithNativeEncodedImage:(const webrtc::EncodedImage &)encodedImage {
   if (self = [super init]) {
     // Wrap the buffer in NSData without copying, do not take ownership.
-    self.buffer = [NSData dataWithBytesNoCopy:encodedImage.data()
+    self.buffer = [NSData dataWithBytesNoCopy:encodedImage.mutable_data()
                                        length:encodedImage.size()
                                  freeWhenDone:NO];
     self.encodedWidth = rtc::dchecked_cast<int32_t>(encodedImage._encodedWidth);