Android video capture: Set camera parameters continuous focus mode on, where supported

This is, apparently, needed for macro modes, although autofocus seems to
work ok in general.

A similar CL was landed and reverted (http://crrev.com/737003003). This CL
is an alternative where the supported focus modes are tested before being
set in the Camera.Parameters.

BUG=343894
TEST=Please refer to the bug, basically a gUM() + close text or QR codes focus test.

Review URL: https://codereview.chromium.org/744193002

Cr-Commit-Position: refs/heads/master@{#305117}

media/base/android/java/src/org/chromium/media/VideoCaptureCamera.java

@@ -165,6 +165,13 @@ public abstract class VideoCaptureCamera extends VideoCapture
             Log.d(TAG, "Image stabilization not supported.");
         }
 
+        if (parameters.getSupportedFocusModes().contains(
+                android.hardware.Camera.Parameters.FOCUS_MODE_CONTINUOUS_VIDEO)) {
+            parameters.setFocusMode(android.hardware.Camera.Parameters.FOCUS_MODE_CONTINUOUS_VIDEO);
+        } else {
+            Log.d(TAG, "Continuous focus mode not supported.");
+        }
+
         setCaptureParameters(matchedWidth, matchedHeight, chosenFrameRate, parameters);
         parameters.setPictureSize(matchedWidth, matchedHeight);
         parameters.setPreviewSize(matchedWidth, matchedHeight);