Truncate test output by kOutputSnippetBytesLimit.

If test output is over kOutputSnippetBytesLimit, which is 300kb, then
TestLauncher::OnTestFinished() trunactes the string to the last 5000
bytes. It looks like this a mix up of kOutputSnippetBytesLimit and
kOutputSnippetLinesLimit.

Bug: 788739
Change-Id: I4aacc4b62f51f764143060bdaeef00031053d1b5
Reviewed-on: https://chromium-review.googlesource.com/809085Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: kylechar <kylechar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#521957}

base/test/launcher/test_launcher.cc

@@ -598,10 +598,11 @@ void TestLauncher::OnTestFinished(const TestResult& original_result) {
   if (result.output_snippet.length() > kOutputSnippetBytesLimit) {
     if (result.status == TestResult::TEST_SUCCESS)
       result.status = TestResult::TEST_EXCESSIVE_OUTPUT;
-    result.output_snippet = StringPrintf(
-        "<truncated (%" PRIuS " bytes)>\n", result.output_snippet.length()) +
-        result.output_snippet.substr(
-            result.output_snippet.length() - kOutputSnippetLinesLimit) +
+    result.output_snippet =
+        StringPrintf("<truncated (%" PRIuS " bytes)>\n",
+                     result.output_snippet.length()) +
+        result.output_snippet.substr(result.output_snippet.length() -
+                                     kOutputSnippetBytesLimit) +
         "\n";
   }