[TaskScheduler]: Use ScopedBlockingCall to mark blocking tasks.

This CL uses ScopedBlockingCall to mark blocking calls in /base/win.

This CL was created by replacing calls to AssertBlockingAllowed()
with instantiations of ScopedBlockingCall(MAY_BLOCK).
I kindly ask the reviewer to make sure of the following:
  - ScopedBlockingCall is instantiated in a scope with minimal CPU usage.
    If this is not the case, ScopedBlockingCall should be instantiated
    closer to the blocking call. See scoped_blocking_call.h for more
    info. Please let me know when/where the blocking call happens if this needs
    to be changed.
  - Parameter |blocking_type| matches expectation (MAY_BLOCK/WILL_BLOCK). See
    BlockingType for more info. While I assumed MAY_BLOCK by default, that might
    not be the best fit if we know that this callsite is guaranteed to block.
  - The ScopedBlockingCall's scope covers the entirety of the blocking operation
    previously asserted against by the AssertBlockingAllowed().

This CL was uploaded by git cl split.

R=grt@chromium.org

Bug: 874080
Change-Id: I0fa6e881ea4b00d0c31b3c8026e095950764a627
Reviewed-on: https://chromium-review.googlesource.com/1191101Reviewed-by: Greg Thompson <grt@chromium.org>
Commit-Queue: Etienne Pierre-Doray <etiennep@chromium.org>
Cr-Commit-Position: refs/heads/master@{#587117}

base/win/shortcut.cc

@@ -11,7 +11,7 @@
 #include <wrl/client.h>
 
 #include "base/files/file_util.h"
-#include "base/threading/thread_restrictions.h"
+#include "base/threading/scoped_blocking_call.h"
 #include "base/win/scoped_propvariant.h"
 #include "base/win/win_util.h"
 #include "base/win/windows_version.h"
@@ -57,7 +57,7 @@ ShortcutProperties::~ShortcutProperties() {
 bool CreateOrUpdateShortcutLink(const FilePath& shortcut_path,
                                 const ShortcutProperties& properties,
                                 ShortcutOperation operation) {
-  AssertBlockingAllowed();
+  ScopedBlockingCall scoped_blocking_call(BlockingType::MAY_BLOCK);
 
   // A target is required unless |operation| is SHORTCUT_UPDATE_EXISTING.
   if (operation != SHORTCUT_UPDATE_EXISTING &&
@@ -199,7 +199,7 @@ bool ResolveShortcutProperties(const FilePath& shortcut_path,
                                uint32_t options,
                                ShortcutProperties* properties) {
   DCHECK(options && properties);
-  AssertBlockingAllowed();
+  ScopedBlockingCall scoped_blocking_call(BlockingType::MAY_BLOCK);
 
   if (options & ~ShortcutProperties::PROPERTIES_ALL)
     NOTREACHED() << "Unhandled property is used.";
@@ -355,7 +355,7 @@ bool CanPinShortcutToTaskbar() {
 }
 
 bool PinShortcutToTaskbar(const FilePath& shortcut) {
-  AssertBlockingAllowed();
+  ScopedBlockingCall scoped_blocking_call(BlockingType::MAY_BLOCK);
   DCHECK(CanPinShortcutToTaskbar());
 
   intptr_t result = reinterpret_cast<intptr_t>(ShellExecute(
@@ -364,7 +364,7 @@ bool PinShortcutToTaskbar(const FilePath& shortcut) {
 }
 
 bool UnpinShortcutFromTaskbar(const FilePath& shortcut) {
-  AssertBlockingAllowed();
+  ScopedBlockingCall scoped_blocking_call(BlockingType::MAY_BLOCK);
 
   intptr_t result = reinterpret_cast<intptr_t>(ShellExecute(
       NULL, L"taskbarunpin", shortcut.value().c_str(), NULL, NULL, 0));