Make tracing work on Android

Previously, the trace coordinator would try to write a trace to the file
system, but it is awkward to write to the file system on Android. Instead, we
now stream the trace data to a data pipe. The Sky debugger consumes that data
pipe and sends it to the host via the command HTTP server.

R=eseidel@chromium.org, jamesr@chromium.org

Review URL: https://codereview.chromium.org/853943005

engine/src/flutter/tools/debugger/prompt/BUILD.gn

@@ -9,12 +9,16 @@ mojo_native_application("prompt") {
 
   sources = [
     "prompt.cc",
+    "trace_collector.cc",
+    "trace_collector.h",
   ]
 
   deps = [
     "//base",
     "//mojo/application",
+    "//mojo/common",
     "//mojo/public/cpp/bindings",
+    "//mojo/public/cpp/system",
     "//mojo/public/cpp/utility",
     "//net",
     "//net:http_server",

engine/src/flutter/tools/debugger/prompt/prompt.cc

@@ -2,7 +2,10 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include <algorithm>
+
 #include "base/bind.h"
+#include "base/files/file_path.h"
 #include "base/memory/weak_ptr.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/stringprintf.h"
@@ -16,11 +19,17 @@
 #include "net/socket/tcp_server_socket.h"
 #include "services/tracing/tracing.mojom.h"
 #include "sky/tools/debugger/debugger.mojom.h"
+#include "sky/tools/debugger/prompt/trace_collector.h"
 
 namespace sky {
 namespace debugger {
+namespace {
 
-class Prompt : public mojo::ApplicationDelegate, public net::HttpServer::Delegate {
+const size_t kMinSendBufferSize = 1024 * 1024;
+}
+
+class Prompt : public mojo::ApplicationDelegate,
+               public net::HttpServer::Delegate {
  public:
   Prompt()
       : is_tracing_(false),
@@ -98,6 +107,10 @@ class Prompt : public mojo::ApplicationDelegate, public net::HttpServer::Delegat
   }
 
   void Respond(int connection_id, std::string response) {
+    // When sending tracing data back over the wire to the client, we can blow
+    // through the default send buffer size.
+    web_server_->SetSendBufferSize(
+        connection_id, std::max(kMinSendBufferSize, response.length()));
     web_server_->Send200(connection_id, response, "text/plain");
   }
 
@@ -138,16 +151,25 @@ class Prompt : public mojo::ApplicationDelegate, public net::HttpServer::Delegat
   }
 
   void ToggleTracing(int connection_id) {
-    std::string response;
-    if (is_tracing_) {
-      response = "Stopping trace (writing to sky_viewer.trace)\n";
-      tracing_->StopAndFlush();
-    } else {
-      response = "Starting trace (type 'trace' to stop tracing)\n";
-      tracing_->Start(mojo::String("sky_viewer"), mojo::String("*"));
-    }
+    bool was_tracing = is_tracing_;
     is_tracing_ = !is_tracing_;
-    Respond(connection_id, response);
+
+    if (was_tracing) {
+      tracing_->StopAndFlush();
+      trace_collector_->GetTrace(base::Bind(
+          &Prompt::OnTraceAvailable, base::Unretained(this), connection_id));
+      return;
+    }
+
+    mojo::DataPipe pipe;
+    tracing_->Start(pipe.producer_handle.Pass(), mojo::String("*"));
+    trace_collector_.reset(new TraceCollector(pipe.consumer_handle.Pass()));
+    Respond(connection_id, "Starting trace (type 'trace' to stop tracing)\n");
+  }
+
+  void OnTraceAvailable(int connection_id, std::string trace) {
+    trace_collector_.reset();
+    Respond(connection_id, trace);
   }
 
   bool is_tracing_;
@@ -158,6 +180,8 @@ class Prompt : public mojo::ApplicationDelegate, public net::HttpServer::Delegat
   scoped_ptr<net::HttpServer> web_server_;
   uint32_t command_port_;
 
+  scoped_ptr<TraceCollector> trace_collector_;
+
   DISALLOW_COPY_AND_ASSIGN(Prompt);
 };
 

engine/src/flutter/tools/debugger/prompt/trace_collector.cc

@@ -0,0 +1,44 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "sky/tools/debugger/prompt/trace_collector.h"
+
+namespace sky {
+namespace debugger {
+
+TraceCollector::TraceCollector(mojo::ScopedDataPipeConsumerHandle source)
+    : drainer_(this, source.Pass()), is_complete_(false) {
+}
+
+TraceCollector::~TraceCollector() {
+}
+
+void TraceCollector::GetTrace(TraceCallback callback) {
+  DCHECK(!callback_.is_null());
+  if (is_complete_) {
+    callback.Run(GetTraceAsString());
+    return;
+  }
+  callback_ = callback;
+}
+
+void TraceCollector::OnDataAvailable(const void* data, size_t num_bytes) {
+  DCHECK(!is_complete_);
+  const char* chars = static_cast<const char*>(data);
+  trace_.insert(trace_.end(), chars, chars + num_bytes);
+}
+
+void TraceCollector::OnDataComplete() {
+  DCHECK(!is_complete_);
+  is_complete_ = true;
+  if (!callback_.is_null())
+    callback_.Run(GetTraceAsString());
+}
+
+std::string TraceCollector::GetTraceAsString() {
+  return std::string(&trace_.front(), trace_.size());
+}
+
+}  // namespace debugger
+}  // namespace sky

engine/src/flutter/tools/debugger/prompt/trace_collector.h

@@ -0,0 +1,40 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef SKY_TOOLS_DEBUGGER_PROMPT_TRACE_COLLECTOR_H_
+#define SKY_TOOLS_DEBUGGER_PROMPT_TRACE_COLLECTOR_H_
+
+#include <vector>
+
+#include "base/callback.h"
+#include "mojo/common/data_pipe_drainer.h"
+
+namespace sky {
+namespace debugger {
+
+class TraceCollector : public mojo::common::DataPipeDrainer::Client {
+ public:
+  typedef base::Callback<void(std::string)> TraceCallback;
+
+  explicit TraceCollector(mojo::ScopedDataPipeConsumerHandle source);
+  ~TraceCollector();
+
+  void GetTrace(TraceCallback callback);
+
+ private:
+  void OnDataAvailable(const void* data, size_t num_bytes) override;
+  void OnDataComplete() override;
+
+  std::string GetTraceAsString();
+
+  mojo::common::DataPipeDrainer drainer_;
+  std::vector<char> trace_;
+  bool is_complete_;
+  TraceCallback callback_;
+};
+
+}  // namespace debugger
+}  // namespace sky
+
+#endif  // SKY_TOOLS_DEBUGGER_PROMPT_TRACE_COLLECTOR_H_