Frameworks: add never sleep screen mode (1/2)

to qs ScreenTimer Tile
to PW ScreenTimer toggle
as general option as well

Change-Id: Ic78356c1b96044562efbce3cb0d0d5c93d773a19

Conflicts:

	packages/SystemUI/res/values/slim_strings.xml
	packages/SystemUI/src/com/android/systemui/statusbar/powerwidget/ScreenTimeoutButton.java
ActivityManager: memoize for performance

isHighEndGfx and isLargeRam are frequently called upon.. isLargeRam very
frequently within the ActivityStack. these aren't going to change after
they're calculated the first time so subject them to a basic memoization.
FTW.

Change-Id: I176089f99ac6c6e4074cb2fde502c729986ea701
Lower the RAM requirement for hardware acceleration

There are legacy devices with about 365 MBytes of RAM
available to the kernel (HDPI with 512 MB RAM onboard).
Lowering the requirement value for available RAM allows
these devices to also use hardware acceleration, thus
making the UI a lot more responsive and fixing bugs like
this: https://dl.dropboxusercontent.com/u/16268774/Screenshots/Phone/Screenshot_2013-10-07-01-27-45.png
(notice the "shadow" is missing)

Conflicts:
	core/java/android/app/ActivityManager.java

Change-Id: I0343ddbb3c7f95bed674b5852772ab819065ea69