Unifying NativeMetafile class interface (as much as possible) for Linux, Mac, Win

printing/pdf_metafile_mac.cc

Index: printing/pdf_metafile_mac.cc
diff --git a/printing/pdf_metafile_mac.cc b/printing/pdf_metafile_mac.cc
index ffd80e8f8d7c765119a5e669e30da4c20fb0a545..50eb1f98a618c0d1afbabfa5dfcec2a308420932 100644
--- a/printing/pdf_metafile_mac.cc
+++ b/printing/pdf_metafile_mac.cc
@@ -20,7 +20,7 @@ PdfMetafile::PdfMetafile()
 
 PdfMetafile::~PdfMetafile() {}
 
-CGContextRef PdfMetafile::Init() {
+bool PdfMetafile::Init() {
   // Ensure that Init hasn't already been called.
   DCHECK(!context_.get());
   DCHECK(!pdf_data_.get());
@@ -28,14 +28,14 @@ CGContextRef PdfMetafile::Init() {
   pdf_data_.reset(CFDataCreateMutable(kCFAllocatorDefault, 0));
   if (!pdf_data_.get()) {
     LOG(ERROR) << "Failed to create pdf data for metafile";
-    return NULL;
+    return false;
   }
   ScopedCFTypeRef<CGDataConsumerRef> pdf_consumer(
       CGDataConsumerCreateWithCFData(pdf_data_));
   if (!pdf_consumer.get()) {
     LOG(ERROR) << "Failed to create data consumer for metafile";
     pdf_data_.reset(NULL);
-    return NULL;
+    return false;
   }
   context_.reset(CGPDFContextCreate(pdf_consumer, NULL, NULL));
   if (!context_.get()) {
@@ -43,7 +43,7 @@ CGContextRef PdfMetafile::Init() {
     pdf_data_.reset(NULL);
   }
 
-  return context_.get();
+  return true;
 }
 
 bool PdfMetafile::Init(const void* src_buffer, uint32 src_buffer_size) {
@@ -84,13 +84,14 @@ CGContextRef PdfMetafile::StartPage(const gfx::Size& page_size,
   return context_.get();
 }
 
-void PdfMetafile::FinishPage() {
+bool PdfMetafile::FinishPage() {
   DCHECK(context_.get());
   DCHECK(page_is_open_);
 
   CGContextRestoreGState(context_);
   CGContextEndPage(context_);
   page_is_open_ = false;
+  return true;
 }
 
 void PdfMetafile::Close() {