Fix a potential crash in Android upon CVC.onAttachedToWindow

This fix a potential bug that can happen, based on the crash report
https://crbug.com/803244. It was not taken into account when landing
https://crrev.com/c/867177.

Bug: 803244
Change-Id: I99c4d927cc69567efae619622ce8baf434cc332b
Reviewed-on: https://chromium-review.googlesource.com/874976
Commit-Queue: Jinsuk Kim <jinsukkim@chromium.org>
Reviewed-by: Bo <boliu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#530419}

content/public/android/java/src/org/chromium/content/browser/ContentViewCoreImpl.java

@@ -588,10 +588,12 @@ public class ContentViewCoreImpl implements ContentViewCore, DisplayAndroidObser
     public void onAttachedToWindow() {
         mAttachedToWindow = true;
         addDisplayAndroidObserverIfNeeded();
-        if (mWebContents != null) updateTextSelectionUI(true);
+        if (mWebContents != null) {
+            updateTextSelectionUI(true);
+            getImeAdapter().onViewAttachedToWindow();
+        }
         GamepadList.onAttachedToWindow(mContext);
         mSystemCaptioningBridge.addListener(this);
-        getImeAdapter().onViewAttachedToWindow();
         mWebContentsAccessibility.onAttachedToWindow();
     }