Validate return code from FPDF_PageToDevice()

A DCHECK() here isn't sufficient to prevent the use of uninitialized
memory should this someday return false.

Bug: 1166091
Change-Id: I4cfd28653f2e6882f227299d68605be706b75b44
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2628044Reviewed-by: K. Moon <kmoon@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#843247}

pdf/pdfium/pdfium_page.cc

@@ -1411,18 +1411,22 @@ gfx::Rect PDFiumPage::PageToScreen(const gfx::Point& page_point,
 
   int new_left;
   int new_top;
-  int new_right;
-  int new_bottom;
-  FPDF_BOOL ret = FPDF_PageToDevice(
+  if (!FPDF_PageToDevice(
           page(), static_cast<int>(start_x), static_cast<int>(start_y),
           static_cast<int>(ceil(size_x)), static_cast<int>(ceil(size_y)),
-      ToPDFiumRotation(orientation), left, top, &new_left, &new_top);
-  DCHECK(ret);
-  ret = FPDF_PageToDevice(
+          ToPDFiumRotation(orientation), left, top, &new_left, &new_top)) {
+    return gfx::Rect();
+  }
+
+  int new_right;
+  int new_bottom;
+  if (!FPDF_PageToDevice(
           page(), static_cast<int>(start_x), static_cast<int>(start_y),
           static_cast<int>(ceil(size_x)), static_cast<int>(ceil(size_y)),
-      ToPDFiumRotation(orientation), right, bottom, &new_right, &new_bottom);
-  DCHECK(ret);
+          ToPDFiumRotation(orientation), right, bottom, &new_right,
+          &new_bottom)) {
+    return gfx::Rect();
+  }
 
   // If the PDF is rotated, the horizontal/vertical coordinates could be
   // flipped.  See