Update DataReductionProxySettings->DataReductionProxyConfig interaction for task runner safety.

- Config is no longer exposed to Settings for purposes of posting the
  "Update Config" task when the UI setting is enabled; instead the call is
  proxied through DRPService to post to DRPIOData on a weak pointer
- Initialization logic updated to ensure DRPService has a weak pointer to
  DRPIOData (initialized on the IO thread), which takes place after DRPIOData
  receives a weak pointer to DRPService (initialized on the UI thread).
- Add DRPService observer so that DRPSettings is notified when DRPService
  receives the DRPIOData weak pointer (so that calls to DRP IO classes will
  not be silently dropped due to the weak pointer not being set).

BUG=472290

Review URL: https://codereview.chromium.org/1075743002

Cr-Commit-Position: refs/heads/master@{#324693}

1 files changed, 2 insertions, 1 deletions

diff --git a/android_webview/browser/aw_browser_context.cc b/android_webview/browser/aw_browser_context.cc
index caa221f..e108895 100644
--- a/android_webview/browser/aw_browser_context.cc
+++ b/android_webview/browser/aw_browser_context.cc
@@ -168,7 +168,8 @@ void AwBrowserContext::PreMainMessageLoopRun() {
       new data_reduction_proxy::DataReductionProxyService(
           scoped_ptr<
               data_reduction_proxy::DataReductionProxyCompressionStats>(),
-          data_reduction_proxy_settings_.get(), GetAwURLRequestContext()));
+          data_reduction_proxy_settings_.get(), GetAwURLRequestContext(),
+          BrowserThread::GetMessageLoopProxyForThread(BrowserThread::IO)));
   data_reduction_proxy_io_data_->SetDataReductionProxyService(
       data_reduction_proxy_service_->GetWeakPtr());