Truncate huge output snippets in the test launcher before printing them

base/test/launcher/test_launcher.cc

Index: base/test/launcher/test_launcher.cc
diff --git a/base/test/launcher/test_launcher.cc b/base/test/launcher/test_launcher.cc
index 8d62afac53a26f9f529c3880a2bb329e95b4478d..d50bf0efa50c7352076704ad7feec5ea24ca68bd 100644
--- a/base/test/launcher/test_launcher.cc
+++ b/base/test/launcher/test_launcher.cc
@@ -76,6 +76,11 @@ const char kUnreliableResultsTag[] = "UNRELIABLE_RESULTS";
 // debugging in case the process hangs anyway.
 const int kOutputTimeoutSeconds = 15;
 
+// Limit of output snippet lines when printing to stdout.
+// Avoids flooding the logs with amount of output that gums up
+// the infrastructure.
+const size_t kOutputSnippetLinesLimit = 50;
+
 // Set of live launch test processes with corresponding lock (it is allowed
 // for callers to launch processes on different threads).
 LazyInstance<std::map<ProcessHandle, CommandLine> > g_live_processes
@@ -451,7 +456,16 @@ void TestLauncher::OnTestFinished(const TestResult& result) {
                  << ": " << print_test_stdio;
   }
   if (print_snippet) {
-    fprintf(stdout, "%s", result.output_snippet.c_str());
+    std::vector<std::string> snippet_lines;

[sky, 2014/06/10 16:25:14]

This initially confused me. I would have thought you wanted the first 50 lines,
but rather you're showing the last. How about a comment?

+    SplitString(result.output_snippet, '\n', &snippet_lines);
+    if (snippet_lines.size() > kOutputSnippetLinesLimit) {
+      size_t truncated_size = snippet_lines.size() - kOutputSnippetLinesLimit;
+      snippet_lines.erase(
+          snippet_lines.begin(),
+          snippet_lines.begin() + truncated_size);
+      snippet_lines.insert(snippet_lines.begin(), "<truncated>");
+    }
+    fprintf(stdout, "%s", JoinString(snippet_lines, "\n").c_str());
     fflush(stdout);
   }