AI 143562: Usability fixes for runtest.py

BUG=1743678

Automated import of CL 143562

testrunner/coverage.py

@@ -70,6 +70,27 @@ class CoverageGenerator(object):
   def EnableCoverageBuild(self):
     """Enable building an Android target with code coverage instrumentation."""
     os.environ[self._EMMA_BUILD_FLAG] = "true"
+    #TODO: can emma.jar automagically be added to bootclasspath here?
+
+  def TestDeviceCoverageSupport(self):
+    """Check if device has support for generating code coverage metrics.
+
+    Currently this will check if the emma.jar file is on the device's boot
+    classpath.
+
+    Returns:
+      True if device can support code coverage. False otherwise.
+    """
+    output = self._adb.SendShellCommand("cat init.rc | grep BOOTCLASSPATH | "
+                                        "grep emma.jar")
+    if len(output) > 0:
+      return True
+    else:
+      logger.Log("Error: Targeted device does not have emma.jar on its "
+                 "BOOTCLASSPATH.")
+      logger.Log("Modify the BOOTCLASSPATH entry in system/core/rootdir/init.rc"
+                 " to add emma.jar")
+      return False
 
   def ExtractReport(self, test_suite,
                     device_coverage_path=_DEVICE_COVERAGE_PATH,