Fix VideoCaptureAndroid, drop frame when switching camera using textures.

Dropping the first frame intended to fix a problem when switching cameras on N6 when we are capturing to textures but due to a silly bug fixed in this cl the frame was not dropped...

BUG=webrtc:5262
TBR=magjed@webrtc.org

Review URL: https://codereview.webrtc.org/1489363002

Cr-Commit-Position: refs/heads/master@{#10867}

talk/app/webrtc/java/android/org/webrtc/VideoCapturerAndroid.java

@@ -745,9 +745,9 @@ public class VideoCapturerAndroid extends VideoCapturer implements
       surfaceHelper.returnTextureFrame();
       return;
     }
-    if (!dropNextFrame)  {
+    if (dropNextFrame)  {
      surfaceHelper.returnTextureFrame();
-     dropNextFrame = true;
+     dropNextFrame = false;
      return;
     }