Reuse PrintContext to excessively triggering matchMedia('print') listeners.

chrome/renderer/print_web_view_helper.cc

Index: chrome/renderer/print_web_view_helper.cc
diff --git a/chrome/renderer/print_web_view_helper.cc b/chrome/renderer/print_web_view_helper.cc
index 4df68f09ebe9fb0d1fea2161c7d888c6ed5e51cc..05b7f42ad5c085510abd233e7ba1c79dd4084dfd 100644
--- a/chrome/renderer/print_web_view_helper.cc
+++ b/chrome/renderer/print_web_view_helper.cc
@@ -372,11 +372,8 @@ PrepareFrameAndViewForPrint::PrepareFrameAndViewForPrint(
     WebFrame* frame,
     const WebNode& node)
         : frame_(frame),
-          node_to_print_(node),
           web_view_(frame->view()),
-          dpi_(static_cast<int>(print_params.dpi)),
           expected_pages_count_(0),
-          use_browser_overlays_(true),
           finished_(false) {
   gfx::Size canvas_size;
   CalculatePrintCanvasSize(print_params, &canvas_size);
@@ -385,7 +382,8 @@ PrepareFrameAndViewForPrint::PrepareFrameAndViewForPrint(
     prev_scroll_offset_ = web_frame->scrollOffset();
   prev_view_size_ = web_view_->size();
 
-  StartPrinting(canvas_size);
+  frame_->printBegin(node);
+  StartPrinting(canvas_size, static_cast<int>(print_params.dpi));
 }
 
 PrepareFrameAndViewForPrint::~PrepareFrameAndViewForPrint() {
@@ -397,17 +395,22 @@ void PrepareFrameAndViewForPrint::UpdatePrintParams(
   DCHECK(!finished_);
   gfx::Size canvas_size;
   CalculatePrintCanvasSize(print_params, &canvas_size);
-  if (canvas_size == print_canvas_size_)
+  int dpi = static_cast<int>(print_params.dpi);
+  if (canvas_size == print_canvas_size_ && dpi == dpi_)
     return;
 
-  frame_->printEnd();
-  dpi_ = static_cast<int>(print_params.dpi);
-  StartPrinting(canvas_size);
+  StartPrinting(canvas_size, dpi);
+}
+
+bool PrepareFrameAndViewForPrint::ShouldUseBrowserOverlays() const {
+    return frame_->shouldUseBrowserOverlays();
 }
 
 void PrepareFrameAndViewForPrint::StartPrinting(
-    const gfx::Size& print_canvas_size) {
+    const gfx::Size& print_canvas_size,
+    int dpi) {
   print_canvas_size_ = print_canvas_size;
+  dpi_ = dpi;
 
   // Layout page according to printer page size. Since WebKit shrinks the
   // size of the page automatically (from 125% to 200%) we trick it to
@@ -420,8 +423,8 @@ void PrepareFrameAndViewForPrint::StartPrinting(
 
   web_view_->resize(print_layout_size);
 
-  expected_pages_count_ = frame_->printBegin(print_canvas_size_, node_to_print_,
-                                             dpi_, &use_browser_overlays_);
+  expected_pages_count_ =
+      frame_->setPageSizeResolution(print_canvas_size_, dpi);
 }
 
 void PrepareFrameAndViewForPrint::FinishPrinting() {
@@ -748,10 +751,6 @@ void PrintWebViewHelper::Print(WebKit::WebFrame* frame,
   if (expected_page_count)
     use_browser_overlays = prepare->ShouldUseBrowserOverlays();
 
-  // Release the prepare before going any further, since we are going to
-  // show UI and wait for the user.
-  prepare.reset();
-
   // Some full screen plugins can say they don't want to print.
   if (!expected_page_count) {
     DidFinishPrinting(OK);  // Release resources and fail silently.
@@ -766,7 +765,7 @@ void PrintWebViewHelper::Print(WebKit::WebFrame* frame,
   }
 
   // Render Pages for printing.
-  if (!RenderPagesForPrint(frame, node, NULL)) {
+  if (!RenderPagesForPrint(frame, node, prepare.get())) {
     LOG(ERROR) << "RenderPagesForPrint failed";
     DidFinishPrinting(FAIL_PRINT);
   }