Fix FPDF_RenderPage 2x zoom in when bBackgroundAlphaNeeded is true

BUG=179413
R=thestig@chromium.org

Review URL: https://codereview.chromium.org/410073002

fpdfsdk/src/fpdfview.cpp

diff --git a/fpdfsdk/src/fpdfview.cpp b/fpdfsdk/src/fpdfview.cpp
index b6b8928..b950ed8 100644
--- a/fpdfsdk/src/fpdfview.cpp
+++ b/fpdfsdk/src/fpdfview.cpp
@@ -458,7 +458,7 @@
 #endif
 	}
 	else
-	pContext->m_pDevice = FX_NEW CFX_WindowsDevice(dc);
+	    pContext->m_pDevice = FX_NEW CFX_WindowsDevice(dc);
 	if (flags & FPDF_NO_CATCH)
 		Func_RenderPage(pContext, page, start_x, start_y, size_x, size_y, rotate, flags,TRUE,NULL);
 	else {
@@ -479,7 +479,7 @@
 				pDst->Create(pBitmap->GetWidth(), pBitmap->GetHeight(),FXDIB_Rgb32);
 				FXSYS_memcpy(pDst->GetBuffer(), pBitmap->GetBuffer(), pBitmap->GetPitch()*pBitmap->GetHeight());
 //				WinDC.SetDIBits(pDst,0,0);
-				WinDC.StretchDIBits(pDst,0,0,size_x*2,size_y*2);
+				WinDC.StretchDIBits(pDst,0,0,size_x,size_y);
 				delete pDst;
  			}
  			else