Bug 756440 - Only try to download crash directory on device if it exists;r=jmaher

Under normal circumstances this should be created automatically inside the
profile directory when we first start, but this won't happen if we fail
to start properly altogether. If that's the case, we've got other problems
that will be reported as errors. Let's just print a warning so we don't
misdiagnose the problem under those circumstances.

build/mobile/remoteautomation.py

@@ -74,13 +74,22 @@ class RemoteAutomation(Automation):
         return status
 
     def checkForCrashes(self, directory, symbolsPath):
-        dumpDir = tempfile.mkdtemp()
-        self._devicemanager.getDirectory(self._remoteProfile + '/minidumps/', dumpDir)
-        automationutils.checkForCrashes(dumpDir, symbolsPath, self.lastTestSeen)
-        try:
-          shutil.rmtree(dumpDir)
-        except:
-          print "WARNING: unable to remove directory: %s" % (dumpDir)
+        remoteCrashDir = self._remoteProfile + '/minidumps/'
+        if self._devicemanager.dirExists(remoteCrashDir):
+            dumpDir = tempfile.mkdtemp()
+            self._devicemanager.getDirectory(remoteCrashDir, dumpDir)
+            automationutils.checkForCrashes(dumpDir, symbolsPath,
+                                            self.lastTestSeen)
+            try:
+                shutil.rmtree(dumpDir)
+            except:
+                print "WARNING: unable to remove directory: %s" % dumpDir
+        else:
+            # As of this writing, the minidumps directory is automatically
+            # created when fennec (first) starts, so its lack of presence
+            # is a hint that something went wrong.
+            print "WARNING: No crash directory (%s) on remote " \
+                "device" % remoteCrashDir
 
     def buildCommandLine(self, app, debuggerInfo, profileDir, testURL, extraArgs):
         # If remote profile is specified, use that instead