Stop camera onStop instead of onPause.

In multi-window mode the non-active activity receives onPause. We
shouldn't stop the camera in this case.

BUG=webrtc:7018

Review-Url: https://codereview.webrtc.org/2648483003
Cr-Commit-Position: refs/heads/master@{#16186}
diff --git a/webrtc/examples/androidapp/src/org/appspot/apprtc/CallActivity.java b/webrtc/examples/androidapp/src/org/appspot/apprtc/CallActivity.java
index 6e94db9..e56d5bc 100644
--- a/webrtc/examples/androidapp/src/org/appspot/apprtc/CallActivity.java
+++ b/webrtc/examples/androidapp/src/org/appspot/apprtc/CallActivity.java
@@ -418,8 +418,8 @@
 
   // Activity interfaces
   @Override
-  public void onPause() {
-    super.onPause();
+  public void onStop() {
+    super.onStop();
     activityRunning = false;
     // Don't stop the video when using screencapture to allow user to show other apps to the remote
     // end.
@@ -430,8 +430,8 @@
   }
 
   @Override
-  public void onResume() {
-    super.onResume();
+  public void onStart() {
+    super.onStart();
     activityRunning = true;
     // Video is not paused for screencapture. See onPause.
     if (peerConnectionClient != null && !screencaptureEnabled) {