Write dm.json periodically instead of only once at the end.

dm/DM.cpp

 #include "CrashHandler.h"
 #include "DMJsonWriter.h"
 #include "DMSrcSink.h"
 #include "OverwriteLine.h"
 #include "ProcStats.h"
 #include "SkBBHFactory.h"
 #include "SkCommonFlags.h"
 #include "SkForceLinking.h"
 #include "SkGraphics.h"
 #include "SkMD5.h"
@@ skipping 27 matching lines @@
 
 static void fail(ImplicitString err) {
     SkAutoMutexAcquire lock(gFailuresMutex);
     SkDebugf("\n\nFAILURE: %s\n\n", err.c_str());
     gFailures.push_back(err);
 }
 
 static int32_t gPending = 0;  // Atomic.
 
 static void done(double ms, ImplicitString config, ImplicitString src, ImplicitString name) {
+    int32_t pending = sk_atomic_dec(&gPending)-1;
     SkDebugf("%s(%4dMB %5d) %s\t%s %s %s  ", FLAGS_verbose ? "\n" : kSkOverwriteLine
                                            , sk_tools::getMaxResidentSetSizeMB()
-                                           , sk_atomic_dec(&gPending)-1
+                                           , pending
                                            , HumanizeMs(ms).c_str()
                                            , config.c_str()
                                            , src.c_str()
                                            , name.c_str());
+    // We write our dm.json file every once in a while in case we crash.
+    // Notice this also handles the final dm.json when pending == 0.
+    if (pending % 500 == 0) {
+        JsonWriter::DumpJson();
+    }
 }
 
 /*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
 
 template <typename T>
 struct Tagged : public SkAutoTDelete<T> { const char* tag; };
 
 static const bool kMemcpyOK = true;
 
 static SkTArray<Tagged<Src>,  kMemcpyOK>  gSrcs;
@@ skipping 378 matching lines @@
                 break;
             default:
                 tg.add(run_enclave, &enclaves[i]);
                 break;
         }
     }
     tg.wait();
     // At this point we're back in single-threaded land.
 
     SkDebugf("\n");
-    JsonWriter::DumpJson();
-
     if (gFailures.count() > 0) {
         SkDebugf("Failures:\n");
         for (int i = 0; i < gFailures.count(); i++) {
             SkDebugf("\t%s\n", gFailures[i].c_str());
         }
         SkDebugf("%d failures\n", gFailures.count());
         return 1;
     }
     if (gPending > 0) {
         SkDebugf("Hrm, we didn't seem to run everything we intended to!  Please file a bug.\n");
         return 1;
     }
     return 0;
 }
 
 #if !defined(SK_BUILD_FOR_IOS) && !defined(SK_BUILD_FOR_NACL)
 int main(int argc, char** argv) {
     SkCommandLineFlags::Parse(argc, argv);
     return dm_main();
 }
 #endif