Extracted a helper library from vie_auto_test.

This CL does not attempt to fix the style issues in the moved tb_ files, at least not yet. In general I've tried to avoid dependencies between the library and vie_auto_test: vie_auto_test depends on the library but not the other way around. I had to make some slight changes to achieve this. I had to remove some ViETest::Log statements in tb_interfaces.cc and I had to move knowledge of where to put output files to the library. I think it ended up being pretty clean in the end but let me know if I missed something. I tried to convert all paths I touched to src-relative paths, so look out if I missed something there.

BUG=
TEST=

Review URL: https://webrtc-codereview.appspot.com/450004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@1923 4adac7df-926f-26a2-2b94-8c16560cd09d

test/testsupport/fileutils.cc

@@ -68,6 +68,16 @@ std::string ProjectRootPath() {
   return kCannotFindProjectRootDir;
 }
 
+#ifdef WEBRTC_ANDROID
+
+std::string OutputPath() {
+  // We need to touch this variable so it doesn't get flagged as unused.
+  (void)kOutputDirName;
+  return "/sdcard/";
+}
+
+#else  // WEBRTC_ANDROID
+
 std::string OutputPath() {
   std::string path = ProjectRootPath();
   if (path == kCannotFindProjectRootDir) {
@@ -80,6 +90,8 @@ std::string OutputPath() {
   return path + kPathDelimiter;
 }
 
+#endif  // !WEBRTC_ANDROID
+
 std::string WorkingDir() {
   char path_buffer[FILENAME_MAX];
   if (!GET_CURRENT_DIR(path_buffer, sizeof(path_buffer))) {