Fixing --verify-predictable mode.

src/libplatform/default-platform.cc

Index: src/libplatform/default-platform.cc
diff --git a/src/libplatform/default-platform.cc b/src/libplatform/default-platform.cc
index 383d8ce1e0dc2d9394521cbc9ce5677890e7674f..dbaec736e8b61e0999cee834910268d37c1cdbaf 100644
--- a/src/libplatform/default-platform.cc
+++ b/src/libplatform/default-platform.cc
@@ -11,6 +11,7 @@
 #include "src/base/platform/platform.h"
 #include "src/base/platform/time.h"
 #include "src/base/sys-info.h"
+#include "src/flags.h"

[Igor Sheludko, 2015/11/10 10:41:06]

Unfortunately this violates "-src" directive from src/libplatform's
include_rules.

 #include "src/libplatform/worker-thread.h"
 
 namespace v8 {
@@ -34,7 +35,7 @@ const int DefaultPlatform::kMaxThreadPoolSize = 4;
 
 
 DefaultPlatform::DefaultPlatform()
-    : initialized_(false), thread_pool_size_(0) {}
+    : initialized_(false), thread_pool_size_(0), synthetic_time_in_sec_(0.0) {}
 
 
 DefaultPlatform::~DefaultPlatform() {
@@ -165,6 +166,11 @@ bool DefaultPlatform::IdleTasksEnabled(Isolate* isolate) { return false; }
 
 
 double DefaultPlatform::MonotonicallyIncreasingTime() {
+  if (v8::internal::FLAG_verify_predictable) {

[Igor Sheludko, 2015/11/10 10:41:06]

We could probably make FLAG_verify_predictable read-only and set it to true when
VERIFY_PREDICTABLE macro is enabled.
Thus we could write #ifdef VERIFY_PREDICTABLE here...

[jochen (gone - plz use gerrit), 2015/11/10 23:20:06]

we can't rely on every embedder doing this. how about just not using this
function in verify predictable mode?

[Igor Sheludko, 2015/11/11 10:20:46]

1) The VERIFY_PREDICTABLE (and then --verify-predictable) is a special build&run
mode that was intended to help us to ensure that we know all sources of
non-determinism in V8 by calculating a hash sum of all allocations. I don't
think the embedders should care about this mode at all. Don't mix it up with
--predictable, which just disables threads and sets random seed.
2) Your idea is fine modulo the fact that several DefaultPlatform's methods also
call MonotonicallyIncreasingTime(), for example
DefaultPlatform::CallDelayedOnForegroundThread().

+    synthetic_time_in_sec_ += 0.000001;
+    return synthetic_time_in_sec_;
+  }
+
   return base::TimeTicks::HighResolutionNow().ToInternalValue() /
          static_cast<double>(base::Time::kMicrosecondsPerSecond);
 }