Hide contaminant dialog "Enable USB" button if not supported

The actual hardware functionality of "Enable USB" depends on USB HAL
capability when Contaminant Detection UI is activated.
When the port does not support enabling/disabling contaminant detection,
the button has no effect other than showing a toast falsely claiming
that USB was enabled.

"Enable USB" should be disabled when USB HAL doesn't support it.

Test: manual; button gone on device lacking disable-detect support
Change-Id: Ib45eef13129f31d5a9d254278ad3c5c3f01db933

packages/SystemUI/src/com/android/systemui/usb/UsbContaminantActivity.java

@@ -75,7 +75,12 @@ public class UsbContaminantActivity extends Activity implements View.OnClickList
             mLearnMore.setVisibility(View.VISIBLE);
         }
 
-        mEnableUsb.setOnClickListener(this);
+        if (!mUsbPort.supportsEnableContaminantPresenceDetection()) {
+            mEnableUsb.setVisibility(View.GONE);
+        } else {
+            mEnableUsb.setOnClickListener(this);
+        }
+
         mGotIt.setOnClickListener(this);
         mLearnMore.setOnClickListener(this);
     }