Revert of Disable the CompilerDispatcher if we don't have idle time (patchset...

Revert of Disable the CompilerDispatcher if we don't have idle time (patchset #1 id:1 of https://codereview.chromium.org/2600743002/ )

Reason for revert:
[Sheriff] Speculative revert since we got persistent timeouts on win32 debug:
https://build.chromium.org/p/client.v8/builders/V8%20Win32%20-%20debug/builds/6417

Please reland if it doesn't help.

Original issue's description:
> Disable the CompilerDispatcher if we don't have idle time
>
> Since we can't do all steps on background threads, we need idle time to
> work
>
> BUG=v8:5215
> R=danno@chromium.org
>
> Review-Url: https://codereview.chromium.org/2600743002
> Cr-Commit-Position: refs/heads/master@{#41944}
> Committed: https://chromium.googlesource.com/v8/v8/+/a0d9eb346bba90aa0b32a2d3184cbbfd6adb243e

TBR=danno@chromium.org,jochen@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=v8:5215

Review-Url: https://codereview.chromium.org/2600773002
Cr-Commit-Position: refs/heads/master@{#41948}

src/compiler-dispatcher/compiler-dispatcher.cc

@@ -110,8 +110,6 @@ CompilerDispatcher::~CompilerDispatcher() {
 }
 
 bool CompilerDispatcher::Enqueue(Handle<SharedFunctionInfo> function) {
-  if (!IsEnabled()) return false;
-
   // We only handle functions (no eval / top-level code / wasm) that are
   // attached to a script.
   if (!function->script()->IsScript() || !function->is_function() ||
@@ -129,11 +127,6 @@ bool CompilerDispatcher::Enqueue(Handle<SharedFunctionInfo> function) {
   return true;
 }
 
-bool CompilerDispatcher::IsEnabled() const {
-  v8::Isolate* v8_isolate = reinterpret_cast<v8::Isolate*>(isolate_);
-  return FLAG_compiler_dispatcher && platform_->IdleTasksEnabled(v8_isolate);
-}
-
 bool CompilerDispatcher::IsEnqueued(Handle<SharedFunctionInfo> function) const {
   return GetJobFor(function) != jobs_.end();
 }
@@ -190,7 +183,7 @@ CompilerDispatcher::JobMap::const_iterator CompilerDispatcher::GetJobFor(
 
 void CompilerDispatcher::ScheduleIdleTaskIfNeeded() {
   v8::Isolate* v8_isolate = reinterpret_cast<v8::Isolate*>(isolate_);
-  DCHECK(platform_->IdleTasksEnabled(v8_isolate));
+  if (!platform_->IdleTasksEnabled(v8_isolate)) return;
   if (idle_task_scheduled_) return;
   if (jobs_.empty()) return;
   idle_task_scheduled_ = true;

src/compiler-dispatcher/compiler-dispatcher.h

@@ -61,7 +61,6 @@ class V8_EXPORT_PRIVATE CompilerDispatcher {
       JobMap;
   class IdleTask;
 
-  bool IsEnabled() const;
   JobMap::const_iterator GetJobFor(Handle<SharedFunctionInfo> shared) const;
   void ScheduleIdleTaskIfNeeded();
   void DoIdleWork(double deadline_in_seconds);

src/flag-definitions.h

@@ -300,7 +300,6 @@ DEFINE_BOOL(string_slices, true, "use string slices")
 DEFINE_BOOL(ignition, false, "use ignition interpreter")
 DEFINE_BOOL(ignition_staging, false, "use ignition with all staged features")
 DEFINE_IMPLICATION(ignition_staging, ignition)
-DEFINE_IMPLICATION(ignition_staging, compiler_dispatcher)
 DEFINE_STRING(ignition_filter, "*", "filter for ignition interpreter")
 DEFINE_BOOL(ignition_deadcode, true,
             "use ignition dead code elimination optimizer")
@@ -667,9 +666,6 @@ DEFINE_BOOL(compilation_cache, true, "enable compilation cache")
 
 DEFINE_BOOL(cache_prototype_transitions, true, "cache prototype transitions")
 
-// compiler-dispatcher.cc
-DEFINE_BOOL(compiler_dispatcher, false, "enable compiler dispatcher")
-
 // cpu-profiler.cc
 DEFINE_INT(cpu_profiler_sampling_interval, 1000,
            "CPU profiler sampling interval in microseconds")

test/unittests/compiler-dispatcher/compiler-dispatcher-unittest.cc

@@ -16,30 +16,7 @@
 namespace v8 {
 namespace internal {
 
-class CompilerDispatcherTest : public TestWithContext {
- public:
-  CompilerDispatcherTest() = default;
-  ~CompilerDispatcherTest() override = default;
-
-  static void SetUpTestCase() {
-    old_flag_ = i::FLAG_ignition;
-    i::FLAG_ignition = true;
-    i::FLAG_compiler_dispatcher = true;
-    TestWithContext::SetUpTestCase();
-  }
-
-  static void TearDownTestCase() {
-    TestWithContext::TearDownTestCase();
-    i::FLAG_ignition = old_flag_;
-  }
-
- private:
-  static bool old_flag_;
-
-  DISALLOW_COPY_AND_ASSIGN(CompilerDispatcherTest);
-};
-
-bool CompilerDispatcherTest::old_flag_;
+typedef TestWithContext CompilerDispatcherTest;
 
 namespace {