Interrogate PpdProvider from PrintPreview.

chrome/browser/ui/webui/print_preview/printer_backend_proxy.cc

Index: chrome/browser/ui/webui/print_preview/printer_backend_proxy.cc
diff --git a/chrome/browser/ui/webui/print_preview/printer_backend_proxy.cc b/chrome/browser/ui/webui/print_preview/printer_backend_proxy.cc
index effbb06c0d45e3532ef7a9dc6ff37666ed58006a..f610f77d33c52b053717e04de93b442f7c4d3a22 100644
--- a/chrome/browser/ui/webui/print_preview/printer_backend_proxy.cc
+++ b/chrome/browser/ui/webui/print_preview/printer_backend_proxy.cc
@@ -52,8 +52,6 @@ std::unique_ptr<base::DictionaryValue> FetchCapabilitiesOnBlockingPool(
   return GetSettingsOnBlockingPool(device_name, basic_info);
 }
 
-}  // namespace
-
 std::string GetDefaultPrinterOnBlockingPoolThread() {
   DCHECK(content::BrowserThread::GetBlockingPool()->RunsTasksOnCurrentThread());
 
@@ -65,21 +63,50 @@ std::string GetDefaultPrinterOnBlockingPoolThread() {
   return default_printer;
 }
 
-void EnumeratePrinters(Profile* /* profile */,
-                       const EnumeratePrintersCallback& cb) {
-  base::PostTaskAndReplyWithResult(
-      content::BrowserThread::GetBlockingPool(), FROM_HERE,
-      base::Bind(&EnumeratePrintersOnBlockingPoolThread), cb);
-}
+// Default implementation of PrinterBackendProxy.  Makes calls directly to
+// the print backend on the appropriate thread.
+class PrinterBackendProxyDefault : public PrinterBackendProxy {
+ public:
+  PrinterBackendProxyDefault() {}
+
+  ~PrinterBackendProxyDefault() override {
+    DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+  }
+
+  void GetDefaultPrinter(const DefaultPrinterCallback& cb) override {
+    DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+
+    base::PostTaskAndReplyWithResult(
+        content::BrowserThread::GetBlockingPool(), FROM_HERE,
+        base::Bind(&GetDefaultPrinterOnBlockingPoolThread), cb);
+  }
 
-void ConfigurePrinterAndFetchCapabilities(Profile* /* profile */,
-                                          const std::string& device_name,
-                                          const PrinterSetupCallback& cb) {
-  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+  void EnumeratePrinters(const EnumeratePrintersCallback& cb) override {
+    DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+
+    base::PostTaskAndReplyWithResult(
+        content::BrowserThread::GetBlockingPool(), FROM_HERE,
+        base::Bind(&EnumeratePrintersOnBlockingPoolThread), cb);
+  }
+
+  void ConfigurePrinterAndFetchCapabilities(
+      const std::string& device_name,
+      const PrinterSetupCallback& cb) override {
+    DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+
+    base::PostTaskAndReplyWithResult(
+        content::BrowserThread::GetBlockingPool(), FROM_HERE,
+        base::Bind(&FetchCapabilitiesOnBlockingPool, device_name), cb);
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(PrinterBackendProxyDefault);
+};
+
+}  // namespace
 
-  base::PostTaskAndReplyWithResult(
-      content::BrowserThread::GetBlockingPool(), FROM_HERE,
-      base::Bind(&FetchCapabilitiesOnBlockingPool, device_name), cb);
+std::unique_ptr<PrinterBackendProxy> PrinterBackendProxy::Create() {
+  return base::MakeUnique<PrinterBackendProxyDefault>();
 }
 
 }  // namespace printing