Prevent TimeUntilNextProcess log spam.

Negative values from TimeUntilNextProcess indicate that the module
wanted to run sooner than possible, not that an invalid error code was
returned. As such it's not a contract error.

BUG=webrtc:4879
NOTRY=true

Review URL: https://codereview.webrtc.org/1257833004

Cr-Commit-Position: refs/heads/master@{#9740}
diff --git a/webrtc/modules/utility/source/process_thread_impl.cc b/webrtc/modules/utility/source/process_thread_impl.cc
index 4ce1675..947fdb0 100644
--- a/webrtc/modules/utility/source/process_thread_impl.cc
+++ b/webrtc/modules/utility/source/process_thread_impl.cc
@@ -25,12 +25,9 @@
 
 int64_t GetNextCallbackTime(Module* module, int64_t time_now) {
   int64_t interval = module->TimeUntilNextProcess();
-  // Currently some implementations erroneously return error codes from
-  // TimeUntilNextProcess(). So, as is, we correct that and log an error.
   if (interval < 0) {
-    LOG(LS_ERROR) << "TimeUntilNextProcess returned an invalid value "
-                  << interval;
-    interval = 0;
+    // Falling behind, we should call the callback now.
+    return time_now;
   }
   return time_now + interval;
 }