PackageManager: Fix concurrent access to shared state

Stop multiple threads from all calling add on the same HashMap.

Cleanup the use of a boolean flag by removing concurrent writes
to it.

Change-Id: I8d61fe7294dcb67ee7d0d7de88d90d2051c310e6
Fix Javadoc link for getModifierBehavior()

Change-Id: I571db5147a081fcd7190483ba9e7a45b46db224d
SpellChecker: bound check for string end

Check whether spell check result is out of end of string
Use strict one to avoid IndexOutOfBoundsException.

Change-Id: I6acac77e1e9750258ed364817a8615a6f56bebe4
[ActivityManager] Ensure consistency behavior when a background activity brings another existed activity to front.

Symptom: ANR occurs on previous activity.
Root Cause:
In KK, when a background activity starts another existed background activity (bring to front),
if current focused stack is not the same as the stack of target starting activity,
it will still resume the top of target stack, even the top activity on the target stack may not the same as target activity.
And it will result incorrect focus, press back key will send to previous stack's top then popup ANR on previous activity:
"Reason: Waiting because no window has focus but there is a focused application".

By original code comment, it looks 'bring to front' should not happen in this issue case.
// If the target task is not in the front, then we need
// to bring it to the front...  except...  well, with
// SINGLE_TASK_LAUNCH it's not entirely clear.  We'd like
// to have the same behavior as if a new instance was
// being started, which means not bringing it to the front
// if the caller is not itself in the front.

If the caller and target are in the same stask, it will just deliver new intent without changing task order (the same behavior as JellyBean).
So the patch concept is just to avoid to use target stack to resume top when caller and target are in different stack.

Solution: Do not allow to resume another stack top if non-top activity try to bring existed activity to front.
It may not be a good solution, just a reminder for the issue case.

Reproduce steps:
Assume A, B, C are different app tasks.
When the application stack is like:
  Top C
      B
      A

 #Case 1: Home is foreground
  A starts B with NEW_TASK, C will resume, focus still stays at Home, and window order does not update.
  Then press back key or volumn key will result ANR on Home.

 #Case 2: App is foreground (Resumed activity is C)
  A starts Home, Home will resume, focus still stays at C, and window order does did not update.
  Then press back key or volumn key will result ANR on C.

Change-Id: If05070123b248e2335791e43a4d4ddee6db11d84