Add a DCHECK for PlatformThread instances that are too busy.

webrtc/base/platform_thread_unittest.cc

Index: webrtc/base/platform_thread_unittest.cc
diff --git a/webrtc/base/platform_thread_unittest.cc b/webrtc/base/platform_thread_unittest.cc
index d6d35e40e4955dfe82367ac29e3ed2de00c1efbf..207a53f2a409ae47958cad391b7910e64552b201 100644
--- a/webrtc/base/platform_thread_unittest.cc
+++ b/webrtc/base/platform_thread_unittest.cc
@@ -17,7 +17,12 @@ namespace rtc {
 namespace {
 // Function that does nothing, and reports success.
 bool NullRunFunctionDeprecated(void* obj) {
-  webrtc::SleepMs(0);  // Hand over timeslice, prevents busy looping.
+  webrtc::SleepMs(2);  // Hand over timeslice, prevents busy looping.
+  return true;
+}
+
+bool TooBusyRunFunction(void* obj) {
+  // Indentionally busy looping.
   return true;
 }
 
@@ -108,4 +113,11 @@ TEST(PlatformThreadTest, RunFunctionIsCalled) {
   EXPECT_TRUE(flag);
 }
 
+TEST(PlatformThreadTest, DISABLED_TooBusyDeprecated) {

[the sun, 2017/03/02 14:20:09]

nit: Can you use DEATH_TEST?

[tommi, 2017/03/02 14:34:55]

I did look into that but couldn't figure out a good way to do that.  The
ASSERT/EXPECT macros require that an expression be set that we expect would
cause the failure, but that code actually happens on another thread which the
test doesn't have direct access to.  There might be some way to do this but I
haven't found it yet.  I put down a TODO for now to look closer.

+  PlatformThread thread(&TooBusyRunFunction, nullptr, "BusyThread");
+  thread.Start();
+  webrtc::SleepMs(1000);
+  thread.Stop();
+}
+
 }  // rtc