Return immediately from GetLogLines if logging to memory isn't enabled.

test/cctest/test-log.cc

Index: test/cctest/test-log.cc
diff --git a/test/cctest/test-log.cc b/test/cctest/test-log.cc
index 0370cbec45196ed67ea1cd790366f40bd996e943..6a7e54f1d11af69765201f6d62a48881dc9b2291 100644
--- a/test/cctest/test-log.cc
+++ b/test/cctest/test-log.cc
@@ -23,6 +23,7 @@ static void TearDown() {
   Logger::TearDown();
 }
 
+
 TEST(EmptyLog) {
   SetUp();
   CHECK_EQ(0, Logger::GetLogLines(0, NULL, 0));
@@ -99,4 +100,18 @@ TEST(BeyondWritePosition) {
   TearDown();
 }
 
+
+TEST(MemoryLoggingTurnedOff) {
+  // Log to stdout
+  v8::internal::FLAG_logfile = "-";
+  v8::internal::FLAG_log = true;
+  Logger::Setup();
+  CHECK_EQ(0, Logger::GetLogLines(0, NULL, 0));
+  CHECK_EQ(0, Logger::GetLogLines(100, NULL, 0));
+  CHECK_EQ(0, Logger::GetLogLines(0, NULL, 100));
+  CHECK_EQ(0, Logger::GetLogLines(100, NULL, 100));
+  Logger::TearDown();
+}
+
+
 #endif  // ENABLE_LOGGING_AND_PROFILING