[Android][Crash] Ensure accessory passes valid content view to UiUtils

Currently, the keyboard accessory uses the focused view in the activity
as view to check for keyboard visibility. This works most of the time,
when an input field is focused but it's thinkable that the focus moves
away (most likely programmatically) which could lead to the observed
crashes.

This CL now ensures, that the focused view is exclusively used when a
keyboard needs to be shown and the detection (which relies on the
content area layout) is always invoked with the content view.

Bug: 876231
Change-Id: Ib65c7985987291cd2b85098b920106dbde40753d
Reviewed-on: https://chromium-review.googlesource.com/1183423Reviewed-by: Theresa <twellington@chromium.org>
Commit-Queue: Friedrich Horschig [CEST] <fhorschig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#584813}

chrome/android/java/src/org/chromium/chrome/browser/autofill/keyboard_accessory/ManualFillingMediator.java

@@ -218,7 +218,7 @@ class ManualFillingMediator
 
     void dismiss() {
         mKeyboardAccessory.dismiss();
-        UiUtils.hideKeyboard(mActivity.getCurrentFocus());
+        if (getContentView() != null) UiUtils.hideKeyboard(getContentView());
     }
 
     void notifyPopupOpened(DropdownPopupWindow popup) {
@@ -239,17 +239,16 @@ class ManualFillingMediator
         mAccessorySheet.setActiveTab(tabIndex);
         if (mPopup != null && mPopup.isShowing()) mPopup.dismiss();
         // If there is a keyboard, update the accessory sheet's height and hide the keyboard.
-        View focusedView = mActivity.getCurrentFocus();
-        if (focusedView != null) {
-            mAccessorySheet.setHeight(calculateAccessorySheetHeight(focusedView.getRootView()));
-            UiUtils.hideKeyboard(focusedView);
+        if (getContentView() != null && getContentView().getRootView() != null) {
+            mAccessorySheet.setHeight(
+                    calculateAccessorySheetHeight(getContentView().getRootView()));
+            UiUtils.hideKeyboard(getContentView());
         }
     }
 
     @Override
     public void onCloseAccessorySheet() {
-        View focusedView = mActivity.getCurrentFocus();
-        if (focusedView == null || UiUtils.isKeyboardShowing(mActivity, focusedView)) {
+        if (getContentView() == null || UiUtils.isKeyboardShowing(mActivity, getContentView())) {
             return; // If the keyboard is showing or is starting to show, the sheet closes gently.
         }
         mActivity.getFullscreenManager().setBottomControlsHeight(mPreviousControlHeight);
@@ -262,7 +261,7 @@ class ManualFillingMediator
     public void onOpenKeyboard() {
         assert mActivity != null : "ManualFillingMediator needs initialization.";
         mActivity.getFullscreenManager().setBottomControlsHeight(calculateAccessoryBarHeight());
-        UiUtils.showKeyboard(mActivity.getCurrentFocus());
+        if (mActivity.getCurrentFocus() != null) UiUtils.showKeyboard(mActivity.getCurrentFocus());
     }
 
     @Override
@@ -275,6 +274,20 @@ class ManualFillingMediator
         mActivity.getFullscreenManager().setBottomControlsHeight(newControlsHeight);
     }
 
+    /**
+     * When trying to get the content of the active tab, there are several cases where a component
+     * can be null - usually use before initialization or after destruction.
+     * This helper ensures that the IDE warns about unchecked use of the all Nullable methods and
+     * provides a shorthand for checking that all components are ready to use.
+     * @return The content {@link View} of the held {@link ChromeActivity} or null if any part of it
+     *         isn't ready to use.
+     */
+    private @Nullable View getContentView() {
+        if (mActivity == null) return null;
+        if (mActivity.getActivityTab() == null) return null;
+        return mActivity.getActivityTab().getContentView();
+    }
+
     private AccessoryState getOrCreateAccessoryState(Tab tab) {
         assert tab != null : "Accessory state was requested without providing a non-null tab!";
         AccessoryState state = mModel.get(tab);