Fix crash on BLU Life Play devices related to switch preferences.

ChromeSwitchPreference uses setWidgetLayoutResource() to show a Material
switch, but on BLU Life Play devices, this has no effect and the default
switch is shown instead. As a result ChromeSwitchPreference.onBindView()
couldn't find the Material switch and was crashing with a NPE. This
fixes the crash by adding a null check, though these devices will still
show a non-material switch.

BUG=451447
R=dtrainor@chromium.org

Review URL: https://codereview.chromium.org/894873004

Cr-Commit-Position: refs/heads/master@{#314250}

chrome/android/java/src/org/chromium/chrome/browser/preferences/ChromeSwitchPreference.java

@@ -50,8 +50,14 @@ public class ChromeSwitchPreference extends SwitchPreference {
     @Override
     protected void onBindView(View view) {
         super.onBindView(view);
+
         ChromeSwitchCompat switchView = (ChromeSwitchCompat) view.findViewById(R.id.switch_widget);
-        switchView.setChecked(isChecked());
+        // On BLU Life Play devices SwitchPreference.setWidgetLayoutResource() does nothing. As a
+        // result, the user will see a non-material Switch and switchView will be null, hence the
+        // null check below. http://crbug.com/451447
+        if (switchView != null) {
+            switchView.setChecked(isChecked());
+        }
 
         TextView title = (TextView) view.findViewById(android.R.id.title);
         title.setSingleLine(false);