DCHECK written counts from fwrite to fix unused return result.

content/browser/tracing/tracing_controller_impl.cc

 // Copyright (c) 2013 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 "content/browser/tracing/tracing_controller_impl.h"
 
 #include "base/bind.h"
 #include "base/debug/trace_event.h"
 #include "base/files/file_util.h"
 #include "base/json/string_escape.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 51 matching lines @@
         base::Bind(&FileTraceDataSink::CloseOnFileThread, this));
   }
 
  private:
   virtual ~FileTraceDataSink() { DCHECK(file_ == NULL); }
 
   void AddTraceChunkOnFileThread(
       const scoped_refptr<base::RefCountedString> chunk) {
     if (!OpenFileIfNeededOnFileThread())
       return;
-    fwrite(chunk->data().c_str(), strlen(chunk->data().c_str()), 1, file_);
+    size_t written = fwrite(chunk->data().c_str(),
+        strlen(chunk->data().c_str()), 1, file_);
+    DCHECK_EQ(1u, written);
   }
 
   bool OpenFileIfNeededOnFileThread() {
     if (file_ != NULL)
       return true;
     file_ = base::OpenFile(file_path_, "w");
     if (file_ == NULL) {
       LOG(ERROR) << "Failed to open " << file_path_.value();
       return false;
     }
     const char preamble[] = "{\"traceEvents\": [";
-    fwrite(preamble, strlen(preamble), 1, file_);
+    size_t written = fwrite(preamble, strlen(preamble), 1, file_);
+    DCHECK_EQ(1u, written);
     return true;
   }
 
   void CloseOnFileThread() {
     if (OpenFileIfNeededOnFileThread()) {
       fputc(']', file_);
       if (!system_trace_.empty()) {
         const char systemTraceEvents[] = ",\"systemTraceEvents\": ";
-        fwrite(systemTraceEvents, strlen(systemTraceEvents), 1, file_);
-        fwrite(system_trace_.c_str(), strlen(system_trace_.c_str()), 1, file_);
+        size_t written = fwrite(systemTraceEvents, strlen(systemTraceEvents),
+            1, file_);
+        DCHECK_EQ(1u, written);
+        written = fwrite(system_trace_.c_str(),
+            strlen(system_trace_.c_str()), 1, file_);
+        DCHECK_EQ(1u, written);
       }
       fputc('}', file_);
       base::CloseFile(file_);
       file_ = NULL;
     }
     BrowserThread::PostTask(
         BrowserThread::UI,
         FROM_HERE,
         base::Bind(&FileTraceDataSink::FinalizeOnUIThread, this));
   }
@@ skipping 766 matching lines @@
   is_monitoring_ = is_monitoring;
 #if !defined(OS_ANDROID)
   for (std::set<TracingUI*>::iterator it = tracing_uis_.begin();
        it != tracing_uis_.end(); it++) {
     (*it)->OnMonitoringStateChanged(is_monitoring);
   }
 #endif
 }
 
 }  // namespace content