Exit after printing usage message.

We should not continue the program if the user asked for help.

Tested on Linux with the following command line:

$ out/Debug/frame_analyzer --help

BUG=None
TEST=see above
R=kjellander@webrtc.org, stefan@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/44069004

Patch from Thiago Farina <tfarina@chromium.org>.

Cr-Commit-Position: refs/heads/master@{#8961}

webrtc/modules/video_coding/codecs/vp8/vp8_sequence_coder.cc

@@ -230,6 +230,7 @@ int main(int argc, char** argv) {
   parser.ProcessFlags();
   if (parser.GetFlag("help") == "true") {
     parser.PrintUsageMessage();
+    exit(EXIT_SUCCESS);
   }
   parser.PrintEnteredFlags();
 

webrtc/tools/converter/rgba_to_i420_converter.cc

@@ -61,6 +61,7 @@ int main(int argc, char** argv) {
   parser.ProcessFlags();
   if (parser.GetFlag("help") == "true") {
     parser.PrintUsageMessage();
+    exit(EXIT_SUCCESS);
   }
   parser.PrintEnteredFlags();
 

webrtc/tools/frame_analyzer/frame_analyzer.cc

@@ -74,6 +74,7 @@ int main(int argc, char** argv) {
   parser.ProcessFlags();
   if (parser.GetFlag("help") == "true") {
     parser.PrintUsageMessage();
+    exit(EXIT_SUCCESS);
   }
   parser.PrintEnteredFlags();
 

webrtc/tools/frame_editing/frame_editing.cc

@@ -77,6 +77,7 @@ int main(int argc, char** argv) {
   parser.ProcessFlags();
   if (parser.GetFlag("help") == "true") {
     parser.PrintUsageMessage();
+    exit(EXIT_SUCCESS);
   }
   parser.PrintEnteredFlags();
 

webrtc/tools/psnr_ssim_analyzer/psnr_ssim_analyzer.cc

@@ -115,6 +115,7 @@ int main(int argc, char** argv) {
   parser.ProcessFlags();
   if (parser.GetFlag("help") == "true") {
     parser.PrintUsageMessage();
+    exit(EXIT_SUCCESS);
   }
   parser.PrintEnteredFlags();