pdfviewer: fix a few warnings

experimental/PdfViewer/SkPdfBasics.h

 #ifndef __DEFINED__SkPdfBasics
 #define __DEFINED__SkPdfBasics
 
 #include "SkCanvas.h"
 #include "SkPaint.h"
 #include "SkPdfConfig.h"
 
 #include <iostream>
 #include <cstdio>
 #include <map>
@@ skipping 38 matching lines @@
     void setRGBColor(SkColor color) {
         // TODO(edisonn): ASSERT DeviceRGB is the color space.
         fColor = color;
     }
     // TODO(edisonn): double check the default values for all fields.
     SkPdfColorOperator() : fColor(SK_ColorBLACK), fOpacity(1) {
         NotOwnedString::init(&fColorSpace);
     }
 
     void applyGraphicsState(SkPaint* paint) {
-        paint->setColor(SkColorSetA(fColor, fOpacity * 255));
+        paint->setColor(SkColorSetA(fColor, (U8CPU)(fOpacity * 255)));
     }
 };
 
 // TODO(edisonn): better class design.
 struct SkPdfGraphicsState {
     // TODO(edisonn): deprecate and remove these!
     double              fCurPosX;
     double              fCurPosY;
 
     double              fCurFontSize;
@@ skipping 296 matching lines @@
     kPartial_PdfResult,
     kNYI_PdfResult,
     kIgnoreError_PdfResult,
     kError_PdfResult,
     kUnsupported_PdfResult,
 
     kCount_PdfResult
 };
 
 #endif  // __DEFINED__SkPdfBasics