Revert "[base] Experiment with only invoking ::PeekMessage when there are pending messages"

This reverts commit d35a8977.

Reason for revert: Causes test failures on Win 7
BUG=chromium:1098531

Original change's description:
> [base] Experiment with only invoking ::PeekMessage when there are pending messages
> 
> ::PeekMessage can process sent-messages and internal events. It seems
> the kernel also uses it as a heuristic to deschedule the main thread when
> it thinks it's out of messages. In MessagePumpForUI's design, it's
> possible to have application tasks without pending native tasks
> (kMsgHaveWork is dropped when running out of native tasks).
> 
> This CL uses ::GetQueueStatus() to probe the presence of messages before
> invoking ::PeekMessage().
> 
> Bug: 1075960
> Change-Id: I4a93b22adf225ae2d62aabeb1a7a734232cf7fb6
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2258456
> Auto-Submit: Gabriel Charette <gab@chromium.org>
> Reviewed-by: François Doray <fdoray@chromium.org>
> Commit-Queue: François Doray <fdoray@chromium.org>
> Commit-Queue: Gabriel Charette <gab@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#781498}

TBR=gab@chromium.org,fdoray@chromium.org

Change-Id: Ib1e700621eef27b1ed8cfd1c50b3019836f6c41b
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1075960
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2262160Reviewed-by: Johann Koenig <johannkoenig@google.com>
Commit-Queue: Johann Koenig <johannkoenig@google.com>
Cr-Commit-Position: refs/heads/master@{#781736}

base/message_loop/message_pump_win.cc

@@ -463,6 +463,10 @@ void MessagePumpForUI::KillNativeTimer() {
 bool MessagePumpForUI::ProcessNextWindowsMessage() {
   DCHECK_CALLED_ON_VALID_THREAD(bound_thread_);
 
+  // If there are sent messages in the queue then PeekMessage internally
+  // dispatches the message and returns false. We return true in this
+  // case to ensure that the message loop peeks again instead of calling
+  // MsgWaitForMultipleObjectsEx.
   bool more_work_is_plausible = false;
   {
     // Individually trace ::GetQueueStatus and ::PeekMessage because sampling
@@ -473,22 +477,7 @@ bool MessagePumpForUI::ProcessNextWindowsMessage() {
     // profiler's thread while the sampled thread is swapped out on this frame).
     TRACE_EVENT0("base",
                  "MessagePumpForUI::ProcessNextWindowsMessage GetQueueStatus");
-
-    // Experiment with querying all messages and not invoking PeekMessage at all
-    // if there's nothing there.
-    static const auto get_queue_status_flag =
-        FeatureList::IsEnabled(kPreventMessagePumpHangs) ? QS_ALLINPUT
-                                                         : QS_SENDMESSAGE;
-
-    const DWORD queue_status = ::GetQueueStatus(get_queue_status_flag);
-
-    if (get_queue_status_flag == QS_ALLINPUT && !queue_status)
-      return false;
-
-    // If there were sent messages in the queue then ::PeekMessage internally
-    // dispatches the message and returns false. We return true in this case to
-    // ensure that the message loop peeks again instead of calling
-    // MsgWaitForMultipleObjectsEx.
+    DWORD queue_status = ::GetQueueStatus(QS_SENDMESSAGE);
     if (HIWORD(queue_status) & QS_SENDMESSAGE)
       more_work_is_plausible = true;
   }
@@ -563,45 +552,32 @@ bool MessagePumpForUI::ProcessPumpReplacementMessage() {
   // that peeked replacement. Note that the re-post of kMsgHaveWork may be
   // asynchronous to this thread!!
 
+  // Bump the work id since ::PeekMessage may process internal events.
+  state_->delegate->BeforeDoInternalWork();
+
+  // The system headers don't define this; it's equivalent to PM_QS_INPUT |
+  // PM_QS_PAINT | PM_QS_POSTMESSAGE. i.e., anything but QS_SENDMESSAGE. Since
+  // we're looking to replace our kMsgHaveWork posted message, we can ignore
+  // sent messages (which never compete with posted messages in the initial
+  // PeekMessage call).
+  constexpr auto PM_QS_ALLEVENTS = QS_ALLEVENTS << 16;
+  static_assert(
+      PM_QS_ALLEVENTS == (PM_QS_INPUT | PM_QS_PAINT | PM_QS_POSTMESSAGE), "");
+  static_assert((PM_QS_ALLEVENTS & PM_QS_SENDMESSAGE) == 0, "");
+
   MSG msg;
   bool have_message = false;
   {
-    // The system headers don't define this; it's equivalent to PM_QS_INPUT |
-    // PM_QS_PAINT | PM_QS_POSTMESSAGE. i.e., anything but QS_SENDMESSAGE. Since
-    // we're looking to replace our kMsgHaveWork posted message, we can ignore
-    // sent messages (which never compete with posted messages in the initial
-    // PeekMessage call).
-    constexpr auto PM_QS_ALLEVENTS = QS_ALLEVENTS << 16;
-    static_assert(
-        PM_QS_ALLEVENTS == (PM_QS_INPUT | PM_QS_PAINT | PM_QS_POSTMESSAGE), "");
-    static_assert((PM_QS_ALLEVENTS & PM_QS_SENDMESSAGE) == 0, "");
+    TRACE_EVENT0("base",
+                 "MessagePumpForUI::ProcessPumpReplacementMessage PeekMessage");
 
     static const auto peek_replacement_message_modifier =
-        FeatureList::IsEnabled(kPreventMessagePumpHangs) ? PM_QS_ALLEVENTS : 0;
-
-    // Always check messages under the non-experimental arm but skip in the
-    // experimental arm if GetQueueStatus() doesn't think there are any.
-    bool check_messages = true;
-    {
-      if (peek_replacement_message_modifier == PM_QS_ALLEVENTS) {
-        TRACE_EVENT0(
-            "base",
-            "MessagePumpForUI::ProcessPumpReplacementMessage GetQueueStatus");
-        check_messages = ::GetQueueStatus(QS_ALLEVENTS);
-      }
-    }
-
-    if (check_messages) {
-      TRACE_EVENT0(
-          "base",
-          "MessagePumpForUI::ProcessPumpReplacementMessage PeekMessage");
+        base::FeatureList::IsEnabled(kPreventMessagePumpHangs) ? PM_QS_ALLEVENTS
+                                                               : 0;
 
-      // Bump the work id since ::PeekMessage may process internal events.
-      state_->delegate->BeforeDoInternalWork();
-      have_message =
-          ::PeekMessage(&msg, nullptr, 0, 0,
-                        PM_REMOVE | peek_replacement_message_modifier) != FALSE;
-    }
+    have_message =
+        ::PeekMessage(&msg, nullptr, 0, 0,
+                      PM_REMOVE | peek_replacement_message_modifier) != FALSE;
   }
 
   // Expect no message or a message different than kMsgHaveWork.