Handle iOS devices with no rear-facing camera

webrtc/api/objc/avfoundationvideocapturer.mm

Index: webrtc/api/objc/avfoundationvideocapturer.mm
diff --git a/webrtc/api/objc/avfoundationvideocapturer.mm b/webrtc/api/objc/avfoundationvideocapturer.mm
index a3f0f44160b2e5c885da1bf6d66a2b9eb142b3d5..fc89fdfc8c638b35729d550790d010b88b1d8220 100644
--- a/webrtc/api/objc/avfoundationvideocapturer.mm
+++ b/webrtc/api/objc/avfoundationvideocapturer.mm
@@ -36,6 +36,7 @@ static cricket::VideoFormat const kDefaultFormat =
 @property(nonatomic, readonly) AVCaptureSession *captureSession;
 @property(nonatomic, readonly) BOOL isRunning;
 @property(nonatomic, assign) BOOL useBackCamera;  // Defaults to NO.
+@property(nonatomic, readonly) BOOL canUseBackCamera;
 
 // We keep a pointer back to AVFoundationVideoCapturer to make callbacks on it
 // when we receive frames. This is safe because this object should be owned by
@@ -88,10 +89,18 @@ static cricket::VideoFormat const kDefaultFormat =
   _capturer = nullptr;
 }
 
+- (BOOL)canUseBackCamera {
+  return _backDeviceInput != nil;
+}
+
 - (void)setUseBackCamera:(BOOL)useBackCamera {
   if (_useBackCamera == useBackCamera) {
     return;
   }
+  if (!self.canUseBackCamera) {
+    NSLog(@"No rear-facing camera exists or it cannot be used; not switching.");
+    return;
+  }
   _useBackCamera = useBackCamera;
   [self updateSessionInput];
 }
@@ -186,10 +195,15 @@ static cricket::VideoFormat const kDefaultFormat =
       frontCaptureDevice = captureDevice;
     }
   }
-  if (!frontCaptureDevice || !backCaptureDevice) {
-    NSLog(@"Failed to get capture devices.");
+  if (!frontCaptureDevice) {
+    NSLog(@"Failed to get front capture device.");
     return NO;
   }
+  if (!backCaptureDevice) {
+    NSLog(@"Failed to get back capture device");
+    // Don't return NO here because devices exist (16GB 5th generation iPod
+    // Touch) that don't have a rear-facing camera.
+  }
 
   // Set up the session inputs.
   NSError *error = nil;
@@ -201,18 +215,21 @@ static cricket::VideoFormat const kDefaultFormat =
           error.localizedDescription);
     return NO;
   }
-  _backDeviceInput =
-      [AVCaptureDeviceInput deviceInputWithDevice:backCaptureDevice
-                                            error:&error];
-  if (!_backDeviceInput) {
-    NSLog(@"Failed to get capture device input: %@",
-          error.localizedDescription);
-    return NO;
+  if (backCaptureDevice) {
+    _backDeviceInput =
+        [AVCaptureDeviceInput deviceInputWithDevice:backCaptureDevice
+                                              error:&error];
+    if (error) {
+      NSLog(@"Failed to get capture device input: %@",
+            error.localizedDescription);
+      _backDeviceInput = nil;
+      error = nil;
+    }
   }
 
   // Add the inputs.
   if (![_captureSession canAddInput:_frontDeviceInput] ||
-      ![_captureSession canAddInput:_backDeviceInput]) {
+      (_backDeviceInput && ![_captureSession canAddInput:_backDeviceInput])) {
     NSLog(@"Session does not support capture inputs.");
     return NO;
   }
@@ -336,6 +353,10 @@ AVCaptureSession* AVFoundationVideoCapturer::GetCaptureSession() {
   return _capturer.captureSession;
 }
 
+bool AVFoundationVideoCapturer::CanUseBackCamera() const {
+  return _capturer.canUseBackCamera;
+}
+
 void AVFoundationVideoCapturer::SetUseBackCamera(bool useBackCamera) {
   _capturer.useBackCamera = useBackCamera;
 }