[wasm] Remove unneeded calls of {RestartBackgroundTasks}

Background tasks are not throttled any more, so there is no need to
restart background compile after finishing units. Background tasks will
only stop if all compilation units have been processed.

R=ahaas@chromium.org

Change-Id: I2b28c079bf5847cd5eb4f65629b9aed89afa8d1e
Reviewed-on: https://chromium-review.googlesource.com/c/1296477Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56909}

src/wasm/module-compiler.cc

@@ -546,9 +546,6 @@ void FinishCompilationUnits(CompilationState* compilation_state,
     // Update the compilation state.
     compilation_state->OnFinishedUnit();
   }
-  if (!compilation_state->failed()) {
-    compilation_state->RestartBackgroundTasks();
-  }
 }
 
 void CompileInParallel(Isolate* isolate, NativeModule* native_module,
@@ -636,7 +633,6 @@ void CompileInParallel(Isolate* isolate, NativeModule* native_module,
   if (!compilation_state->failed() &&
       compilation_state->compile_mode() == CompileMode::kTiering) {
     compilation_state->SetFinisherIsRunning(false);
-    compilation_state->RestartBackgroundTasks();
   }
 }
 
@@ -2973,7 +2969,6 @@ void CompilationState::OnFinishedUnit() {
     // If we are in {kRegular} mode, {num_tiering_units_} is 0, therefore
     // this case is already caught by the previous check.
     NotifyOnEvent(CompilationEvent::kFinishedBaselineCompilation, nullptr);
-    RestartBackgroundTasks();
   }
 }