arc: Stop waiting for crash reporter on UI thread

components/arc/crash_collector/arc_crash_collector_bridge.cc

Index: components/arc/crash_collector/arc_crash_collector_bridge.cc
diff --git a/components/arc/crash_collector/arc_crash_collector_bridge.cc b/components/arc/crash_collector/arc_crash_collector_bridge.cc
index 8557308a6b87703c0994a97aa5dbbffd3c395439..4d915a01e0e37ef90a9f6ddde82f43834657c94c 100644
--- a/components/arc/crash_collector/arc_crash_collector_bridge.cc
+++ b/components/arc/crash_collector/arc_crash_collector_bridge.cc
@@ -14,13 +14,29 @@
 #include "mojo/edk/embedder/embedder.h"
 
 namespace {
+
 const char kCrashReporterPath[] = "/sbin/crash_reporter";
+
+// Waits for the process to exit.
+void WaitForProcessToExit(base::Process process) {
+  int exit_code = 0;
+  if (!process.WaitForExit(&exit_code)) {
+    LOG(ERROR) << "Failed to wait for " << kCrashReporterPath;
+  } else if (exit_code != EX_OK) {
+    LOG(ERROR) << kCrashReporterPath << " failed with exit code " << exit_code;
+  }
+}
+
 }
 
 namespace arc {
 
-ArcCrashCollectorBridge::ArcCrashCollectorBridge(ArcBridgeService* bridge)
-    : ArcService(bridge), binding_(this) {
+ArcCrashCollectorBridge::ArcCrashCollectorBridge(
+    ArcBridgeService* bridge,
+    scoped_refptr<base::TaskRunner> blocking_task_runner)
+    : ArcService(bridge),
+      blocking_task_runner_(blocking_task_runner),
+      binding_(this) {
   arc_bridge_service()->crash_collector()->AddObserver(this);
 }
 
@@ -51,13 +67,9 @@ void ArcCrashCollectorBridge::DumpCrash(const mojo::String& type,
                            "--arc_device=" + device_, "--arc_board=" + board_,
                            "--arc_cpu_abi=" + cpu_abi_},
                           options);
-
-  int exit_code;
-  if (!process.WaitForExit(&exit_code)) {
-    LOG(ERROR) << "Failed to wait for " << kCrashReporterPath;
-  } else if (exit_code != EX_OK) {
-    LOG(ERROR) << kCrashReporterPath << " failed with exit code " << exit_code;
-  }
+  blocking_task_runner_->PostTask(FROM_HERE,

[hidehiko, 2016/09/26 14:17:22]

Optional: How about moving everything, incl. LaunchProcess, to blocking task
runner? It looks ok to do, according to the client side code.

[hashimoto, 2016/09/27 06:48:26]

Done.

+                                  base::Bind(&WaitForProcessToExit,
+                                             base::Passed(std::move(process))));
 }
 
 void ArcCrashCollectorBridge::SetBuildProperties(const mojo::String& device,