[TaskScheduler]: Use ScopedBlockingCall to mark blocking tasks.

This CL uses ScopedBlockingCall to mark blocking calls in /chrome/browser/shell_integration_win.cc.

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=gab@chromium.org

Bug: 874080
Change-Id: Ifa0f35aa3000ab99401647c45a131b3c457eeb8c
Reviewed-on: https://chromium-review.googlesource.com/1191095
Commit-Queue: Etienne Pierre-Doray <etiennep@chromium.org>
Reviewed-by: Patrick Monette <pmonette@chromium.org>
Reviewed-by: Gabriel Charette <gab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#594749}

chrome/browser/shell_integration_win.cc

@@ -31,6 +31,7 @@
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/task/post_task.h"
+#include "base/threading/scoped_blocking_call.h"
 #include "base/time/time.h"
 #include "base/timer/timer.h"
 #include "base/win/registry.h"
@@ -144,8 +145,6 @@ base::string16 GetExpectedAppId(const base::CommandLine& command_line,
 }
 
 void MigrateTaskbarPinsCallback() {
-  base::AssertBlockingAllowed();
-
   // Get full path of chrome.
   base::FilePath chrome_exe;
   if (!base::PathService::Get(base::FILE_EXE, &chrome_exe))
@@ -323,8 +322,6 @@ class OpenSystemSettingsHelper {
   // watched. The array must contain at least one element.
   static void Begin(const wchar_t* const protocols[],
                     const base::Closure& on_finished_callback) {
-    base::AssertBlockingAllowed();
-
     delete instance_;
     instance_ = new OpenSystemSettingsHelper(protocols, on_finished_callback);
   }
@@ -527,7 +524,7 @@ void IsPinnedToTaskbarHelper::OnIsPinnedToTaskbarResult(
 }  // namespace
 
 bool SetAsDefaultBrowser() {
-  base::AssertBlockingAllowed();
+  base::ScopedBlockingCall scoped_blocking_call(base::BlockingType::MAY_BLOCK);
 
   base::FilePath chrome_exe;
   if (!base::PathService::Get(base::FILE_EXE, &chrome_exe)) {
@@ -547,7 +544,7 @@ bool SetAsDefaultBrowser() {
 }
 
 bool SetAsDefaultProtocolClient(const std::string& protocol) {
-  base::AssertBlockingAllowed();
+  base::ScopedBlockingCall scoped_blocking_call(base::BlockingType::MAY_BLOCK);
 
   if (protocol.empty())
     return false;
@@ -628,7 +625,7 @@ DefaultWebClientState IsDefaultProtocolClient(const std::string& protocol) {
 namespace win {
 
 bool SetAsDefaultBrowserUsingIntentPicker() {
-  base::AssertBlockingAllowed();
+  base::ScopedBlockingCall scoped_blocking_call(base::BlockingType::MAY_BLOCK);
 
   base::FilePath chrome_exe;
   if (!base::PathService::Get(base::FILE_EXE, &chrome_exe)) {
@@ -647,8 +644,6 @@ bool SetAsDefaultBrowserUsingIntentPicker() {
 
 void SetAsDefaultBrowserUsingSystemSettings(
     const base::Closure& on_finished_callback) {
-  base::AssertBlockingAllowed();
-
   base::FilePath chrome_exe;
   if (!base::PathService::Get(base::FILE_EXE, &chrome_exe)) {
     NOTREACHED() << "Error getting app exe path";
@@ -673,7 +668,7 @@ void SetAsDefaultBrowserUsingSystemSettings(
 }
 
 bool SetAsDefaultProtocolClientUsingIntentPicker(const std::string& protocol) {
-  base::AssertBlockingAllowed();
+  base::ScopedBlockingCall scoped_blocking_call(base::BlockingType::MAY_BLOCK);
 
   base::FilePath chrome_exe;
   if (!base::PathService::Get(base::FILE_EXE, &chrome_exe)) {
@@ -695,8 +690,6 @@ bool SetAsDefaultProtocolClientUsingIntentPicker(const std::string& protocol) {
 void SetAsDefaultProtocolClientUsingSystemSettings(
     const std::string& protocol,
     const base::Closure& on_finished_callback) {
-  base::AssertBlockingAllowed();
-
   base::FilePath chrome_exe;
   if (!base::PathService::Get(base::FILE_EXE, &chrome_exe)) {
     NOTREACHED() << "Error getting app exe path";