tools: use '/usr/bin/env python' instead of '/usr/bin/python'

* This is how it is done in other scripts in the AOSP tree, as
  '/usr/bin/python' may be python3 on some distros, which isn't
  supported yet.

Change-Id: I0d9857fc6a122f505953fddcd6244dad75b1838a
runtime: Invert the default for dexopt-on-cache

The growth of /system apps and total /data space are making this
device-breaking (insufficient space to dexopt everything to
/cache), pointless (/data has more than enough room to hold
the cache), and in some cases, both.
The default behavior is now the same as mainline Android's: dexopt
everything to /data. Set dalvik.vm.dexopt-data-only=0 to change
that and dexopt /system apps to /cache. If you do that, make sure
your /cache can accomodate double the size of the dex classes in
system, since that has been observed during dex2oat

Change-Id: I8c1debee6e16a6fb162e42a7c9a47ec076eb69df
Finish fixing Zygote descriptor leakage problem

In order to prevent Zygote descriptors from leaking into the child
environment, they should be closed by the forked-off child process
before the child switches to the application UID.  These changes close
the descriptors via dup2(), substituting a descriptor open to
/dev/null in their place; this allows the Zygote Java code to close
the FileDescriptor objects cleanly.

This is a multi-project change:	dalvik, art, libcore, frameworks/base,
and external/sepolicy are affected.  The CLs need to be approved
together, lest the build break or the software fail to boot.

Round 2: use proper type (jsize) for iteration variable;  whitespace.

Round 3: indentation.

Bug: 12114500
Change-Id: I31d25831b477b076d980c531d57773f9c8c83261
Remove old fork-and-specialize API

As promised, this is the cleanup patch-set which removes the
old native "fork and specialize" API, which has been replaced
by a slightly-enhanced one which can close the Zygote socket
descriptors in the Zygote child.

Change-Id: I096f058e851aa079e342ecc718ff5757db68c8cd
Fix NewLocalRef, NewGlobalRef to handle cleared weak globals.

We were not checking for null after decoding the reference, this
meant that we incorrectly created null weak global references instead
of returning null.

Issue: 63929
Change-Id: I9159682e6edad8f415ef8144fc13b9aedd2cceb4