Reland "[filesapp] Add missing includes and fail if host crashed"

This reverts commit 6e991fa7

Reason for revert: MSAN error that caused the original revert was
fixed on CL:2466572.

Original change's description:
> Revert "[filesapp] Add missing includes and fail if host crashed"
>
> This reverts commit 4734ecf2.
>
> Reason for revert: https://crrev.com/c/2461602 breaks build Linux ChromiumOS MSan Tests in https://ci.chromium.org/p/chromium/builders/ci/Linux%20ChromiumOS%20MSan%20Tests/20900
> Failed test is DevToolsListenerBrowserTest.CanCollectCodeCoverage
>
> Original change's description:
> > [filesapp] Add missing includes and fail if host crashed
> >
> > Adds #include's that were missing from the initial patch, and FAIL the
> > test if the DevToolsAgentHost attached to crashes during the test.
> >
> > Fix HostString() helper to *actually* take an optional prefix: use C++
> > c++17 {} style initializer.
> >
> > Test: browser_test --gtest_filter="*DevToolsListener*"
> > Bug: 1113941
> > Change-Id: I5901019add9fea92b6e3a8b5b881b8d3d197b6c0
> > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2465456
> > Commit-Queue: Ben Reich <benreich@chromium.org>
> > Reviewed-by: Noel Gordon <noel@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#816070}
>
> TBR=noel@chromium.org,benreich@chromium.org
>
> Change-Id: I87ec9b3db970807af8fc75ca137fc83397f775bf
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug: 1113941
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2466016
> Reviewed-by: Maggie Cai <mxcai@chromium.org>
> Commit-Queue: Maggie Cai <mxcai@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#816400}

TBR=noel@chromium.org,mxcai@chromium.org,benreich@chromium.org

# Not skipping CQ checks because this is a reland.

Bug: 1113941
Change-Id: I10432537826bc0ecd3938230b8454a9f1dbd8cfd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2465900
Commit-Queue: Noel Gordon <noel@chromium.org>
Reviewed-by: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#816490}

chrome/browser/chromeos/file_manager/devtools_listener.cc

@@ -72,7 +72,7 @@ void DevToolsListener::Detach(content::DevToolsAgentHost* host) {
 }
 
 std::string DevToolsListener::HostString(content::DevToolsAgentHost* host,
-                                         const std::string& prefix = "") {
+                                         const std::string& prefix) {
   std::string result = base::StrCat(
       {prefix, " ", host->GetType(), " title: ", host->GetTitle()});
   std::string description = host->GetDescription();

chrome/browser/chromeos/file_manager/devtools_listener.h

@@ -42,7 +42,7 @@ class DevToolsListener : public content::DevToolsAgentHostClient {
   // Returns a string that uniquely identifies a host
   // with an optional prefix.
   static std::string HostString(content::DevToolsAgentHost* host,
-                                const std::string& prefix);
+                                const std::string& prefix = {});
 
  private:
   // Enable CDP on host.

chrome/browser/chromeos/file_manager/devtools_listener_browsertest.cc

@@ -3,16 +3,20 @@
 // found in the LICENSE file.
 
 #include <map>
+#include <memory>
 
 #include "base/files/file_util.h"
+#include "base/files/scoped_temp_dir.h"
 #include "base/path_service.h"
 #include "base/process/process_handle.h"
+#include "base/threading/thread_restrictions.h"
 #include "chrome/browser/chromeos/file_manager/devtools_listener.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "chrome/common/chrome_paths.h"
 #include "chrome/test/base/in_process_browser_test.h"
 #include "chrome/test/base/ui_test_utils.h"
+#include "content/public/browser/devtools_agent_host.h"
 #include "content/public/browser/devtools_agent_host_observer.h"
 #include "content/public/test/browser_test.h"
 #include "content/public/test/browser_test_utils.h"
@@ -55,7 +59,7 @@ class DevToolsListenerBrowserTest : public content::DevToolsAgentHostObserver,
                                 base::TerminationStatus status) override {
     if (devtools_agent_.find(host) == devtools_agent_.end())
       return;
-    NOTREACHED();
+    LOG(FATAL) << "Host crashed: " << DevToolsListener::HostString(host);
   }
 
   void CollectCodeCoverage() {