Improve error handling for js2gtest C++ generation.

Previously, an error in a javascript file would cause the error to be written
to the -gen.cc file and fed to the C++ compiler (rarely accepts such
output as valid C++).  This change causes the generation build action to fail
and the error to be output to the stderr of the ninja process instead.
Also, stack traces are improved by annotating eval'd files with sourceURL
comments when running the generator.

BUG=None

Review URL: https://codereview.chromium.org/1299893002

Cr-Commit-Position: refs/heads/master@{#345964}

1 files changed, 3 insertions, 0 deletions

diff --git a/tools/gypv8sh.py b/tools/gypv8sh.py
index 2a1fada..d1f246c 100755
--- a/tools/gypv8sh.py
+++ b/tools/gypv8sh.py
@@ -65,6 +65,9 @@ def main ():
       p = subprocess.Popen(
           cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE, bufsize=0)
       out, err = p.communicate()
+      if p.returncode != 0:
+        sys.stderr.write(out + err);
+        return 1
       if not HasSameContent(cxxoutfile, out):
         with open(cxxoutfile, 'wb') as f:
           f.write(out)