[TaskScheduler]: Migrate off of AssertBlockingAllowedDeprecated in /android_webview

base::AssertBlockingAllowedDeprecated is deprecated in favor of
ScopedBlockingCall, which serves as a precise annotation of
the scope that may/will block.

Please 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: The call might block (e.g. file I/O that might hit in memory cache).
      WILL_BLOCK: The call will definitely block (e.g. cache already checked and now pinging
        server synchronously).
    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().
  - Calls to blocking //base APIs don't need to be annotated
    with ScopedBlockingCall. All blocking //base APIs (e.g. base::ReadFileToString, base::File::Read,
    base::SysInfo::AmountOfFreeDiskSpace, base::WaitableEvent::Wait, etc.) have their
    own internal annotations.

Refer to the top-level CL if necessary :
https://chromium-review.googlesource.com/c/chromium/src/+/1338391

Please CQ if LGTY!

This CL was uploaded by git cl split.

R=torne@chromium.org

Bug: 903957
Change-Id: Iaf80012bf6f5c5f7852031c21f68c75e11957ca1
Reviewed-on: https://chromium-review.googlesource.com/c/1338481Reviewed-by: Richard Coles <torne@chromium.org>
Commit-Queue: Etienne Pierre-Doray <etiennep@chromium.org>
Cr-Commit-Position: refs/heads/master@{#608869}

android_webview/browser/aw_contents_io_thread_client.cc

@@ -17,6 +17,7 @@
 #include "base/containers/flat_set.h"
 #include "base/lazy_instance.h"
 #include "base/synchronization/lock.h"
+#include "base/threading/scoped_blocking_call.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/render_frame_host.h"
 #include "content/public/browser/render_process_host.h"
@@ -342,7 +343,7 @@ namespace {
 std::unique_ptr<AwWebResourceResponse> RunShouldInterceptRequest(
     const AwWebResourceRequest& request,
     JavaObjectWeakGlobalRef ref) {
-  base::AssertBlockingAllowedDeprecated();
+  base::ScopedBlockingCall scoped_blocking_call(base::BlockingType::MAY_BLOCK);
 
   JNIEnv* env = AttachCurrentThread();
   base::android::ScopedJavaLocalRef<jobject> obj = ref.get(env);

android_webview/browser/aw_variations_service_client.cc

@@ -6,7 +6,7 @@
 
 #include "android_webview/common/aw_channel.h"
 #include "base/bind.h"
-#include "base/threading/thread_restrictions.h"
+#include "base/threading/scoped_blocking_call.h"
 #include "build/build_config.h"
 #include "services/network/public/cpp/shared_url_loader_factory.h"
 
@@ -18,7 +18,7 @@ namespace {
 // Gets the version number to use for variations seed simulation. Must be called
 // on a thread where IO is allowed.
 base::Version GetVersionForSimulation() {
-  base::AssertBlockingAllowedDeprecated();
+  base::ScopedBlockingCall scoped_blocking_call(base::BlockingType::MAY_BLOCK);
   return version_info::GetVersion();
 }