Printing: Fix undefined behavior for near 0 scaling

components/printing/renderer/print_web_view_helper.cc

Index: components/printing/renderer/print_web_view_helper.cc
diff --git a/components/printing/renderer/print_web_view_helper.cc b/components/printing/renderer/print_web_view_helper.cc
index 3e77142273bf41af06906e9d9f0b6a56ea6718b5..70198bfc77afbac453930f708b6240755b8205be 100644
--- a/components/printing/renderer/print_web_view_helper.cc
+++ b/components/printing/renderer/print_web_view_helper.cc
@@ -234,7 +234,7 @@ void CalculatePageLayoutFromPrintParams(
   int content_height = params.content_size.height();
   // Scale the content to its normal size for purpose of computing page layout.
   // Otherwise we will get negative margins.
-  if (scale_factor > 0 && (fit_to_page || params.print_to_pdf)) {
+  if (scale_factor >= 0.01f && (fit_to_page || params.print_to_pdf)) {

[Lei Zhang, 2016/10/29 00:26:53]

Add a constexpr double kEpsilon constant and use that everywhere.

[rbpotter, 2016/10/29 00:41:53]

Done.

     content_width =
         static_cast<int>(static_cast<double>(content_width) * scale_factor);
     content_height =
@@ -721,7 +721,7 @@ PrepareFrameAndViewForPrint::PrepareFrameAndViewForPrint(
     frame->printBegin(web_print_params_, node_to_print_);
     double scale_factor = 1.0f;
 #if defined(ENABLE_PRINT_PREVIEW)
-    if (print_params.scale_factor > 0)
+    if (print_params.scale_factor >= 0.01f)
       scale_factor = print_params.scale_factor;
 #endif
     print_params = CalculatePrintParamsForCss(
@@ -1232,7 +1232,7 @@ bool PrintWebViewHelper::CreatePreviewDocument() {
 
   PageSizeMargins default_page_layout;
   double scale_factor =
-      print_params.scale_factor > 0 ? print_params.scale_factor : 1.0f;
+      print_params.scale_factor >= 0.01f ? print_params.scale_factor : 1.0f;
 
   ComputePageLayoutInPointsForCss(print_preview_context_.prepared_frame(), 0,
                                   print_params, ignore_css_margins_,
@@ -1828,7 +1828,7 @@ void PrintWebViewHelper::PrintPageInternal(
 
   double css_scale_factor = 1.0f;
 #if defined(ENABLE_PRINT_PREVIEW)
-    if (params.params.scale_factor > 0)
+    if (params.params.scale_factor >= 0.01f)
       css_scale_factor = params.params.scale_factor;
 #endif
   ComputePageLayoutInPointsForCss(frame, params.page_number, params.params,