Introduce test output snippet byte limit

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 e6880fa54f5f462acb4c3050e78b2f3f143a8885..fae0307287adc6e9369b1bf7e1d8b3e07072b683 100644
--- a/base/test/launcher/test_launcher.cc
+++ b/base/test/launcher/test_launcher.cc
@@ -90,6 +90,10 @@ const int kOutputTimeoutSeconds = 15;
 // the infrastructure.
 const size_t kOutputSnippetLinesLimit = 5000;
 
+// Limit of output snippet size. Exceeding this limit
+// results in truncating the output and failing the test.
+const size_t kOutputSnippetBytesLimit = 10 * 1024 * 1024;
+
 // 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
@@ -568,9 +572,17 @@ void TestLauncher::LaunchChildGTestProcess(
            launched_callback));
 }
 
-void TestLauncher::OnTestFinished(const TestResult& result) {
+void TestLauncher::OnTestFinished(const TestResult& original_result) {
   ++test_finished_count_;
 
+  TestResult result(original_result);
+
+  if (result.output_snippet.length() > kOutputSnippetBytesLimit) {
+    if (result.status == TestResult::TEST_SUCCESS)
+      result.status = TestResult::TEST_EXCESSIVE_OUTPUT;
+    result.output_snippet = "<truncated>\n";

[Dirk Pranke, 2016/10/12 23:33:27]

Maybe this should include at least some of the snippet? 

Also, it seems like even 10MB is much too generous, I would want to understand
why any test would need more than a KB or two of output. But, it's fine to start
high and ratchet down.

[Paweł Hajdan Jr., 2016/10/13 14:55:59]

Done.
It turns out (tested on trybots) we need 2.5 MB limit. I'll probably work on
reducing that. Only a limited number of tests are affected.

+  }
+
   bool print_snippet = false;
   std::string print_test_stdio("auto");
   if (CommandLine::ForCurrentProcess()->HasSwitch(