Update flutter runner process name to reflect last running shell. (fl…

…utter#5102)

content_handler/application.cc

@@ -163,6 +163,10 @@ Application::Application(
 
 Application::~Application() = default;
 
+const std::string& Application::GetDebugLabel() const {
+  return debug_label_;
+}
+
 void Application::AttemptVMLaunchWithCurrentSettings(
     const blink::Settings& settings) const {
   if (blink::DartVM::ForProcessIfInitialized()) {

content_handler/application.h

@@ -49,6 +49,8 @@ class Application final : public Engine::Delegate,
   // may be collected after.
   ~Application();
 
+  const std::string& GetDebugLabel() const;
+
  private:
   blink::Settings settings_;
   Delegate& delegate_;

content_handler/application_runner.cc

@@ -4,28 +4,59 @@
 
 #include "application_runner.h"
 
+#include <zircon/types.h>
+
+#include <sstream>
 #include <utility>
 
 #include "flutter/lib/ui/text/font_collection.h"
 #include "fuchsia_font_manager.h"
-#include "third_party/skia/include/core/SkGraphics.h"
 #include "lib/icu_data/cpp/icu_data.h"
+#include "third_party/skia/include/core/SkGraphics.h"
 
 namespace flutter {
 
+static void SetProcessName(const std::string& process_name) {
+  zx::process::self().set_property(ZX_PROP_NAME, process_name.c_str(),
+                                   process_name.size());
+}
+
+static void SetThreadName(const std::string& thread_name) {
+  zx::thread::self().set_property(ZX_PROP_NAME, thread_name.c_str(),
+                                  thread_name.size());
+}
+
+static void SetProcessName(const std::string& label, size_t app_count) {
+  // Format: "flutter.<label_truncated_to_fit>+<app_count>"
+  //         "flutter" in case of error.
+
+  const std::string prefix = "flutter.";
+  const std::string suffix =
+      app_count == 0 ? "" : "+" + std::to_string(app_count);
+
+  if ((prefix.size() + suffix.size()) > ZX_MAX_NAME_LEN) {
+    SetProcessName("flutter");
+    return;
+  }
+
+  auto truncated_label =
+      label.substr(0, ZX_MAX_NAME_LEN - 1 - (prefix.size() + suffix.size()));
+
+  SetProcessName(prefix + truncated_label + suffix);
+}
+
 ApplicationRunner::ApplicationRunner(fxl::Closure on_termination_callback)
     : on_termination_callback_(std::move(on_termination_callback)),
       host_context_(component::ApplicationContext::CreateFromStartupInfo()) {
-
   SkGraphics::Init();
 
   SetupICU();
 
   SetupGlobalFonts();
 
-  const std::string process_label = "flutter";
-  zx::process::self().set_property(ZX_PROP_NAME, process_label.c_str(),
-                                   process_label.size());
+  SetProcessName("application_runner", 0);
+
+  SetThreadName("io.flutter.application_runner");
 
   host_context_->outgoing_services()->AddService<component::ApplicationRunner>(
       std::bind(&ApplicationRunner::RegisterApplication, this,
@@ -55,6 +86,12 @@ void ApplicationRunner::StartApplication(
                           std::move(startup_info),  // startup info
                           std::move(controller)     // controller request
       );
+
+  // Update the process label so that "ps" will will list the last appication
+  // started by the runner plus the count of applications hosted by this runner.
+  SetProcessName(thread_application_pair.second->GetDebugLabel(),
+                 active_applications_.size());
+
   active_applications_[thread_application_pair.second.get()] =
       std::move(thread_application_pair);
 }