enable -Wstring-conversion when compiling with clang

ppapi/examples/video_decode/video_decode.cc

 // Copyright (c) 2012 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 <string.h>
 
 #include <iostream>
 #include <sstream>
 #include <list>
 #include <map>
@@ skipping 52 matching lines @@
   // pp::Instance implementation (see PPP_Instance).
   virtual void DidChangeView(const pp::Rect& position,
                              const pp::Rect& clip_ignored);
 
   // pp::Graphics3DClient implementation.
   virtual void Graphics3DContextLost() {
     // TODO(vrk/fischman): Properly reset after a lost graphics context.  In
     // particular need to delete context_ and re-create textures.
     // Probably have to recreate the decoder from scratch, because old textures
     // can still be outstanding in the decoder!
-    assert(!"Unexpectedly lost graphics context");
+    assert(false && "Unexpectedly lost graphics context");
   }
 
   // pp::VideoDecoderClient_Dev implementation.
   virtual void ProvidePictureBuffers(
       PP_Resource decoder,
       uint32_t req_num_of_bufs,
       const PP_Size& dimensions,
       uint32_t texture_target);
   virtual void DismissPictureBuffer(PP_Resource decoder,
                                     int32_t picture_buffer_id);
@@ skipping 370 matching lines @@
   pp::CompletionCallback cb =
       callback_factory_.NewCallback(
           &VideoDecodeDemoInstance::PaintFinished, decoder, info.buffer.id);
   last_swap_request_ticks_ = core_if_->GetTimeTicks();
   assert(context_->SwapBuffers(cb) == PP_OK_COMPLETIONPENDING);
 }
 
 void VideoDecodeDemoInstance::NotifyError(PP_Resource decoder,
                                           PP_VideoDecodeError_Dev error) {
   LogError(this).s() << "Received error: " << error;
-  assert(!"Unexpected error; see stderr for details");
+  assert(false && "Unexpected error; see stderr for details");
 }
 
 // This object is the global object representing this plugin library as long
 // as it is loaded.
 class VideoDecodeDemoModule : public pp::Module {
  public:
   VideoDecodeDemoModule() : pp::Module() {}
   virtual ~VideoDecodeDemoModule() {}
 
   virtual pp::Instance* CreateInstance(PP_Instance instance) {
@@ skipping 200 matching lines @@
   gles2_if_->DeleteShader(context_->pp_resource(), shader);
 }
 }  // anonymous namespace
 
 namespace pp {
 // Factory function for your specialization of the Module object.
 Module* CreateModule() {
   return new VideoDecodeDemoModule();
 }
 }  // namespace pp