No longer clamp setTimeout(..., 0) to 1ms.

third_party/WebKit/Source/core/frame/DOMTimerTest.cpp

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/frame/DOMTimer.h"
 
 #include <vector>
 
 #include "bindings/core/v8/ScriptController.h"
 #include "bindings/core/v8/ScriptSourceCode.h"
 #include "bindings/core/v8/V8Binding.h"
 #include "core/dom/Document.h"
 #include "core/layout/LayoutTestHelper.h"
 #include "platform/testing/TestingPlatformSupport.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 using testing::DoubleNear;
 using testing::ElementsAreArray;
 using testing::Matcher;
 
 namespace blink {
 
 namespace {
 
+const double kThreshold = 0.000001;
+
 class DOMTimerTest : public RenderingTest {
  public:
   ScopedTestingPlatformSupport<TestingPlatformSupportWithMockScheduler>
       platform_;
 
   // Expected time between each iterator for setInterval(..., 1) or nested
   // setTimeout(..., 1) are 1, 1, 1, 1, 4, 4, ... as a minumum clamp of 4m
   // is applied from the 5th iteration onwards.
   const std::vector<Matcher<double>> kExpectedTimings = {
-      DoubleNear(1., 0.000001), DoubleNear(1., 0.000001),
-      DoubleNear(1., 0.000001), DoubleNear(1., 0.000001),
-      DoubleNear(4., 0.000001), DoubleNear(4., 0.000001),
+      DoubleNear(1., kThreshold), DoubleNear(1., kThreshold),
+      DoubleNear(1., kThreshold), DoubleNear(1., kThreshold),
+      DoubleNear(4., kThreshold), DoubleNear(4., kThreshold),
   };
 
   void SetUp() override {
     platform_->SetAutoAdvanceNowToPendingTasks(true);
     // Advance timer manually as RenderingTest expects the time to be non-zero.
     platform_->AdvanceClockSeconds(1.);
     RenderingTest::SetUp();
     // Advance timer again as otherwise the time between the first call to
     // setInterval and it running will be off by 5us.
     platform_->AdvanceClockSeconds(1);
     GetDocument().GetSettings()->SetScriptEnabled(true);
   }
 
   v8::Local<v8::Value> EvalExpression(const char* expr) {
     return GetDocument()
         .GetFrame()
         ->Script()
         .ExecuteScriptInMainWorldAndReturnValue(ScriptSourceCode(expr));
   }
 
   Vector<double> ToDoubleArray(v8::Local<v8::Value> value,
                                v8::HandleScope& scope) {
     NonThrowableExceptionState exception_state;
     return ToImplArray<Vector<double>>(value, 0, scope.GetIsolate(),
                                        exception_state);
   }
 
+  double ToDoubleValue(v8::Local<v8::Value> value, v8::HandleScope& scope) {
+    NonThrowableExceptionState exceptionState;
+    return ToDouble(scope.GetIsolate(), value, exceptionState);
+  }
+
   void ExecuteScriptAndWaitUntilIdle(const char* script_text) {
     ScriptSourceCode script(script_text);
     GetDocument().GetFrame()->Script().ExecuteScriptInMainWorld(script);
     platform_->RunUntilIdle();
   }
 };
 
-const char* g_k_set_timeout_script_text =
-    "var id;"
+const char* const kSetTimeout0ScriptText =
+    "var last = performance.now();"
+    "var elapsed;"
+    "function setTimeoutCallback() {"
+    "  var current = performance.now();"
+    "  elapsed = current - last;"
+    "  times.push(elapsed);"
+    "}"
+    "setTimeout(setTimeoutCallback, 0);";
+
+TEST_F(DOMTimerTest, setTimeout_ZeroIsNotClampedToOne) {
+  v8::HandleScope scope(v8::Isolate::GetCurrent());
+
+  ExecuteScriptAndWaitUntilIdle(kSetTimeout0ScriptText);
+
+  double time = ToDoubleValue(EvalExpression("elapsed"), scope);
+
+  EXPECT_THAT(time, DoubleNear(0., kThreshold));
+}
+
+const char* const kSetTimeoutNestedScriptText =
     "var last = performance.now();"
     "var times = [];"
     "function nestSetTimeouts() {"
     "  var current = performance.now();"
     "  var elapsed = current - last;"
     "  last = current;"
     "  times.push(elapsed);"
     "  if (times.length < 6) {"
     "    setTimeout(nestSetTimeouts, 1);"
     "  }"
     "}"
     "setTimeout(nestSetTimeouts, 1);";
 
 TEST_F(DOMTimerTest, setTimeout_ClampsAfter4Nestings) {
   v8::HandleScope scope(v8::Isolate::GetCurrent());
 
-  ExecuteScriptAndWaitUntilIdle(g_k_set_timeout_script_text);
+  ExecuteScriptAndWaitUntilIdle(kSetTimeoutNestedScriptText);
 
   auto times(ToDoubleArray(EvalExpression("times"), scope));
 
   EXPECT_THAT(times, ElementsAreArray(kExpectedTimings));
 }
 
-const char* g_k_set_interval_script_text =
+const char* const kSetIntervalScriptText =
     "var last = performance.now();"
     "var times = [];"
     "var id = setInterval(function() {"
     "  var current = performance.now();"
     "  var elapsed = current - last;"
     "  last = current;"
     "  times.push(elapsed);"
     "  if (times.length > 5) {"
     "    clearInterval(id);"
     "  }"
     "}, 1);";
 
 TEST_F(DOMTimerTest, setInterval_ClampsAfter4Iterations) {
   v8::HandleScope scope(v8::Isolate::GetCurrent());
 
-  ExecuteScriptAndWaitUntilIdle(g_k_set_interval_script_text);
+  ExecuteScriptAndWaitUntilIdle(kSetIntervalScriptText);
 
   auto times(ToDoubleArray(EvalExpression("times"), scope));
 
   EXPECT_THAT(times, ElementsAreArray(kExpectedTimings));
 }
 
 TEST_F(DOMTimerTest, setInterval_NestingResetsForLaterCalls) {
   v8::HandleScope scope(v8::Isolate::GetCurrent());
 
-  ExecuteScriptAndWaitUntilIdle(g_k_set_interval_script_text);
+  ExecuteScriptAndWaitUntilIdle(kSetIntervalScriptText);
 
   // Run the setIntervalScript again to verify that the clamp imposed for
   // nesting beyond 4 levels is reset when setInterval is called again in the
   // original scope but after the original setInterval has completed.
-  ExecuteScriptAndWaitUntilIdle(g_k_set_interval_script_text);
+  ExecuteScriptAndWaitUntilIdle(kSetIntervalScriptText);
 
   auto times(ToDoubleArray(EvalExpression("times"), scope));
 
   EXPECT_THAT(times, ElementsAreArray(kExpectedTimings));
 }
 
 }  // namespace
 
 }  // namespace blink