Use given trace file directly if the temp file doesn't work

Fall back to the old behavior of just writing to a trace file directly
if we're unable to open a temporary file in the same directory. This can
happen in some configurations on restrictive Android systems for
example, where the browser may only be able to write to the actual file
specified in --trace-startup-file, and not to any nearby path.

Bug: 1082916
Change-Id: I3c1275b4c70cc8edb6e50adc321ba412c6226de8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2346352Reviewed-by: Eric Seckler <eseckler@chromium.org>
Commit-Queue: Tomasz Śniatowski <tsniatowski@vewd.com>
Cr-Commit-Position: refs/heads/master@{#796735}

content/browser/tracing/tracing_controller_impl_data_endpoint.cc

@@ -90,14 +90,20 @@ class FileTraceDataEndpoint : public TracingController::TraceDataEndpoint {
 
     // The temporary trace file is produced in the same folder since paths must
     // be on the same volume.
-    file_ = FileToFILE(CreateAndOpenTemporaryFileInDir(file_path_.DirName(),
-                                                       &pending_file_path_),
-                       "w");
-    if (file_ == nullptr) {
-      LOG(ERROR) << "Failed to open " << file_path_.value();
-      return false;
+    base::File temp_file = CreateAndOpenTemporaryFileInDir(file_path_.DirName(),
+                                                           &pending_file_path_);
+    if (temp_file.IsValid()) {
+      file_ = FileToFILE(std::move(temp_file), "w");
+    } else {
+      LOG(WARNING) << "Unable to use temporary file " << pending_file_path_
+                   << ": "
+                   << base::File::ErrorToString(temp_file.error_details());
+      pending_file_path_.clear();
+      file_ = base::OpenFile(file_path_, "w");
+      LOG_IF(ERROR, file_ == nullptr)
+          << "Failed to open " << file_path_.value();
     }
-    return true;
+    return file_ != nullptr;
   }
 
   void CloseOnBlockingThread() {
@@ -106,6 +112,7 @@ class FileTraceDataEndpoint : public TracingController::TraceDataEndpoint {
       file_ = nullptr;
     }
 
+    if (!pending_file_path_.empty()) {
       base::File::Error error;
       if (!base::ReplaceFile(pending_file_path_, file_path_, &error)) {
         LOG(ERROR) << "Cannot replace file '" << file_path_
@@ -113,6 +120,7 @@ class FileTraceDataEndpoint : public TracingController::TraceDataEndpoint {
         base::DeleteFile(pending_file_path_);
         return;
       }
+    }
 
     GetUIThreadTaskRunner({})->PostTask(
         FROM_HERE,