SamplingProfilerIntegration and SamplingProfiler improvements (3/3)

Summary:

frameworks/base
- fix profiling to collect data beyond the first snapshot
- avoid many small files, accumulate data over process lifetime

libcore:
- add support for VM specific sampling, trying to cut down overhead
- added support for converting snapshot files to text format
- fixed race in profiler when stopping

dalvik
- added VMStack.setThreadStackTrace interface for filling a stack
  trace into an existing StackTraceElement[]

Details:

frameworks/base

    Changed snapshots from text to binary hprof format (bumping version to 3)
    Changed from one file per snapshot to one file per process lifetime.
    Restart profiling after snapshot.

	core/java/com/android/internal/os/SamplingProfilerIntegration.java

    Add quick test in maybeSnapshot to avoid doing work when the
    SamplingProfilerIntegration is disabled. Make maybeSnapshot
    private. Remove unneeded memory allocation in handleLowMemory.

	core/java/android/app/ActivityThread.java

libcore

    Added ThreadSampler interface. This allows VM specific thread
    sampling optimizations. The portable version continues to use
    Thread.getStackTrace().

	dalvik/src/main/java/dalvik/system/profiler/ThreadSampler.java
	dalvik/src/main/java/dalvik/system/profiler/PortableThreadSampler.java
	dalvik/src/main/java/dalvik/system/profiler/SamplingProfiler.java

    Add VMStack.setThreadStackTrace and use in new DalvikThreadSampler
    to avoid allocating a full stack trace when only a limited depth
    is desired.

	dalvik/src/main/java/dalvik/system/profiler/DalvikThreadSampler.java
	dalvik/src/main/java/dalvik/system/VMStack.java

    Refactored BinaryHprof.readMagic out of BinaryHprofReader so it
    can be used by HprofBinaryToAscii converter to probing file
    types. Added magic number constant to be shared between readMagic
    and BinaryHprofWriter.

	dalvik/src/main/java/dalvik/system/profiler/BinaryHprof.java
	dalvik/src/main/java/dalvik/system/profiler/BinaryHprofReader.java
	dalvik/src/main/java/dalvik/system/profiler/BinaryHprofWriter.java
	dalvik/src/main/java/dalvik/system/profiler/HprofBinaryToAscii.java

    Removed unneeded HprofWriter interface. Changed to simpler static
    interface to write HprofData to binary and text formats.

	dalvik/src/main/java/dalvik/system/profiler/HprofWriter.java
	dalvik/src/main/java/dalvik/system/profiler/AsciiHprofWriter.java
	dalvik/src/main/java/dalvik/system/profiler/BinaryHprofWriter.java
	dalvik/src/test/java/dalvik/system/profiler/SamplingProfilerTest.java

    Added support for reading snapshot files created by
    SamplingProfilerIntegration by stripping the text header to allow
    easier conversion to the text format.

	dalvik/src/main/java/dalvik/system/profiler/HprofBinaryToAscii.java

    Fixed race between Sampler and
    SamplingProfiler.stop. SamplingProfiler.stop previously simply
    called the Sampler's TimerTask.cancel method, but this does not
    wait for a currently running Sampler to finish. The TimerTask
    documentation says the only reliable way to do this is to have the
    run() cancel itself, so that is what is now done, with new code to
    ensure that SamplingProfiler.stop does not return until the
    Sampler has been terminated.

	dalvik/src/main/java/dalvik/system/profiler/SamplingProfiler.java

dalvik

   Refactored VMStack_getThreadStackTrace to create helper getTraceBuf
   used to implement new VMStack_setThreadStackTrace. The new version
   interface fills an existing StackTraceElement[], avoid allocating
   unnecessary StackTraceElements.

	vm/native/dalvik_system_VMStack.c

   Refactor dvmGetStackTraceRaw to create dvmSetStackTraceRaw which
   fills in an existing, potentially smaller, StackTraceElement[].

	vm/Exception.c
	vm/Exception.h

   Change stack depths to be unsigned to avoid signed/unsigned comparison warnings.

	vm/Ddm.c
	vm/Exception.c
	vm/Exception.h

Change-Id: I4b90255e4e1d33ea2b569321c4968b0f3369f251