Bug 775071 - Fix testCheck3 to abort the test if the disableScreenshto function fails. r=gbrown

mobile/android/base/tests/testCheck3.java.in

@@ -15,7 +15,13 @@ public class testCheck3 extends PixelTest {
         // Disable Fennec's low-res screenshot for the duration of this test;
         // this distinguishes this test from testCheck2, which is otherwise
         // identical.
-        disableScreenshot();
+        if (!disableScreenshot()) {
+            // if disabling the screenshot fails, there is no point in running
+            // this test, so abort. the lack of __start_report output from the
+            // end of the test should get picked up as an error by the talos
+            // harness.
+            return;
+        }
 
         mActions.expectGeckoEvent("Gecko:Ready").blockForEvent();
         loadAndPaint(url);
@@ -55,12 +61,13 @@ public class testCheck3 extends PixelTest {
         mAsserter.dumpLog("__startTimestamp" + msecs + "__endTimestamp");
     }
 
-    private void disableScreenshot() {
+    private boolean disableScreenshot() {
         try {
             ClassLoader classLoader = getActivity().getClassLoader();
             Class appshell = classLoader.loadClass("org.mozilla.gecko.GeckoAppShell");
             Method disableScreenshotMethod = appshell.getMethod("disableScreenshot");
             disableScreenshotMethod.invoke(null);
+            return true;
         } catch (ClassNotFoundException ex) {
             mAsserter.ok(false, "Error getting class", ex.toString());
         } catch (IllegalAccessException ex) {
@@ -70,5 +77,6 @@ public class testCheck3 extends PixelTest {
         } catch (java.lang.reflect.InvocationTargetException ex) {
             mAsserter.ok(false, "Error invoking method", ex.toString());
         }
+        return false;
     }
 }