Allow incoming SMS until internal storage is almost full.

Fix for bug 2382830: new incoming SMS should not be rejected when
running low on internal phone storage.

Testing revealed that the /data partition should have at least 256 KiB
available in order to prevent random app crashes (including system apps)
due to SQLite transaction failures. With 256 KiB free, the device should
safely boot without storage full errors. This takes into account the
36-40 KiB that the YAFFS2 filesystem reports as available even after
the partition has been completely filled. I've set the default full
threshold to 1 MiB to provide a generous safety margin.

For this bug, I changed the DeviceStorageMonitorService demon to send
two new hidden notifications for device storage "full" and "not full",
when the free space falls below the full threshold (default 1 MiB,
but configurable as a system setting), in addition to the existing
storage low/okay notifications sent when the storage crosses the threshold
of 90% full (also configurable).

The SMS code was changed to use these new notifications so that it can
accept messages until the data partition has been filled to the maximum
safe capacity rather than stopping when it hits 90% full. There should
be no negative impact on battery life because the additional check in
the storage polling service should be offset by an optimization to cache
the free threshold values which were previously being computed every time
through the loop.

While testing this change, I discovered that SMSDispatcher was being
instantiated twice, the first time in GSMPhone/CDMAPhone, and the second
time in SimSmsInterfaceManager / RuimSmsInterfaceManager. Changed the code
to pass the original SMSDispatcher to the Sim/RuimSmsInterfaceManager
constructor.

Change-Id: Ie0c6d05294778ab6ee42e0fa01313af96d824c77
10 files changed