Add support for running host java tests to runtest.

With this change, also refactored runtest as follows: Modified the
test suite schema and python implementation to have an inheritance
structure.  Each test type has its own python module, which will
also handle the logic of running the test.

testrunner/adb_interface.py

@@ -306,7 +306,7 @@ class AdbInterface:
     attempts = 0
     wait_period = 5
     while not pm_found and (attempts*wait_period) < wait_time:
-      # assume the 'adb shell pm path android' command will always 
+      # assume the 'adb shell pm path android' command will always
       # return 'package: something' in the success case
       output = self.SendShellCommand("pm path android", retry_count=1)
       if "package:" in output:
@@ -357,12 +357,12 @@ class AdbInterface:
 
   def Sync(self, retry_count=3):
     """Perform a adb sync.
-    
+
     Blocks until device package manager is responding.
-    
+
     Args:
       retry_count: number of times to retry sync before failing
-      
+
     Raises:
       WaitForResponseTimedOutError if package manager does not respond
       AbortError if unrecoverable error occurred
@@ -375,12 +375,12 @@ class AdbInterface:
       error = e
       output = e.msg
     if "Read-only file system" in output:
-      logger.SilentLog(output) 
+      logger.SilentLog(output)
       logger.Log("Remounting read-only filesystem")
       self.SendCommand("remount")
       output = self.SendCommand("sync", retry_count=retry_count)
     elif "No space left on device" in output:
-      logger.SilentLog(output) 
+      logger.SilentLog(output)
       logger.Log("Restarting device runtime")
       self.SendShellCommand("stop", retry_count=retry_count)
       output = self.SendCommand("sync", retry_count=retry_count)
@@ -392,3 +392,7 @@ class AdbInterface:
     self.WaitForDevicePm()
     return output
 
+  def GetSerialNumber(self):
+    """Returns the serial number of the targeted device."""
+    return self.SendCommand("get-serialno").strip()
+