Remove the unused CipherKeyActivity

chrome/android/java/AndroidManifest.xml

Index: chrome/android/java/AndroidManifest.xml
diff --git a/chrome/android/java/AndroidManifest.xml b/chrome/android/java/AndroidManifest.xml
index a374a2ca2880bd007da8a2c6718a640f228d7c21..840ff9764ecfe0e901360abfbdb04a9f5c85749b 100644
--- a/chrome/android/java/AndroidManifest.xml
+++ b/chrome/android/java/AndroidManifest.xml
@@ -540,15 +540,6 @@ by a child template that "extends" this file.
             android:excludeFromRecents="true">
         </activity>
 
-        <!-- This activity is started along with IncognitoDocumentActivity, so it also must
-             disable hardware acceleration. Besides, it doesn't have any UI. -->
-        <activity android:name="org.chromium.chrome.browser.document.CipherKeyActivity"
-            android:launchMode="singleInstance"
-            android:theme="@android:style/Theme.Translucent.NoTitleBar"
-            android:excludeFromRecents="true"
-            android:hardwareAccelerated="false">
-        </activity>
-
         <!-- This activity is used to restart the main Chrome process.  Should never be exported. -->
         <activity android:name="org.chromium.chrome.browser.BrowserRestartActivity"
             android:launchMode="singleInstance"