Log disabled warning when autofill triggered.

Currently, we issue the warning log when webview is created, it is
hard to tell which webview's autofill is disabled, changed to log the
warning when autofill is triggered.

Bug: 
Change-Id: I4fa480db7f8d825f29b980b44c80add732c35407
Reviewed-on: https://chromium-review.googlesource.com/794528Reviewed-by: Changwan Ryu <changwan@chromium.org>
Commit-Queue: Tao Bai <michaelbai@chromium.org>
Cr-Commit-Position: refs/heads/master@{#520225}

android_webview/java/src/org/chromium/android_webview/AwAutofillManager.java

@@ -43,13 +43,12 @@ public class AwAutofillManager {
     private boolean mIsAutofillInputUIShowing;
     private AutofillInputUIMonitor mMonitor;
     private boolean mDestroyed;
+    private boolean mDisabled;
 
     public AwAutofillManager(Context context) {
         if (DEBUG) Log.i(TAG, "constructor");
         if (AwContents.activityFromContext(context) == null) {
-            Log.w(TAG,
-                    "WebView autofill is disabled because WebView isn't created with "
-                            + "activity context.");
+            mDisabled = true;
             return;
         }
         mAutofillManager = context.getSystemService(AutofillManager.class);
@@ -58,56 +57,63 @@ public class AwAutofillManager {
     }
 
     public void notifyVirtualValueChanged(View parent, int childId, AutofillValue value) {
-        if (isDestroyed() || mAutofillManager == null) return;
+        if (mDisabled || checkAndWarnIfDestroyed()) return;
         if (DEBUG) Log.i(TAG, "notifyVirtualValueChanged");
         mAutofillManager.notifyValueChanged(parent, childId, value);
     }
 
     public void commit() {
-        if (isDestroyed() || mAutofillManager == null) return;
+        if (mDisabled || checkAndWarnIfDestroyed()) return;
         if (DEBUG) Log.i(TAG, "commit");
         mAutofillManager.commit();
     }
 
     public void cancel() {
-        if (isDestroyed() || mAutofillManager == null) return;
+        if (mDisabled || checkAndWarnIfDestroyed()) return;
         if (DEBUG) Log.i(TAG, "cancel");
         mAutofillManager.cancel();
     }
 
     public void notifyVirtualViewEntered(View parent, int childId, Rect absBounds) {
-        if (isDestroyed() || mAutofillManager == null) return;
+        // Log warning only when the autofill is triggered.
+        if (mDisabled) {
+            Log.w(TAG,
+                    "WebView autofill is disabled because WebView isn't created with "
+                            + "activity context.");
+            return;
+        }
+        if (checkAndWarnIfDestroyed()) return;
         if (DEBUG) Log.i(TAG, "notifyVirtualViewEntered");
         mAutofillManager.notifyViewEntered(parent, childId, absBounds);
     }
 
     public void notifyVirtualViewExited(View parent, int childId) {
-        if (isDestroyed() || mAutofillManager == null) return;
+        if (mDisabled || checkAndWarnIfDestroyed()) return;
         if (DEBUG) Log.i(TAG, "notifyVirtualViewExited");
         mAutofillManager.notifyViewExited(parent, childId);
     }
 
     public void requestAutofill(View parent, int virtualId, Rect absBounds) {
-        if (isDestroyed() || mAutofillManager == null) return;
+        if (mDisabled || checkAndWarnIfDestroyed()) return;
         if (DEBUG) Log.i(TAG, "requestAutofill");
         mAutofillManager.requestAutofill(parent, virtualId, absBounds);
     }
 
     public boolean isAutofillInputUIShowing() {
-        if (isDestroyed() || mAutofillManager == null) return false;
+        if (mDisabled || checkAndWarnIfDestroyed()) return false;
         if (DEBUG) Log.i(TAG, "isAutofillInputUIShowing: " + mIsAutofillInputUIShowing);
         return mIsAutofillInputUIShowing;
     }
 
     public void destroy() {
-        if (isDestroyed() || mAutofillManager == null) return;
+        if (mDisabled || checkAndWarnIfDestroyed()) return;
         if (DEBUG) Log.i(TAG, "destroy");
         mAutofillManager.unregisterCallback(mMonitor);
         mAutofillManager = null;
         mDestroyed = true;
     }
 
-    private boolean isDestroyed() {
+    private boolean checkAndWarnIfDestroyed() {
         if (mDestroyed) {
             Log.w(TAG, "Application attempted to call on a destroyed AwAutofillManager",
                     new Throwable());