dom: base: nsDocument: Let view port size adapt display size

So all kinds of web site can fit the content view correctly in both
desktop mode and mobile mode.

Also revert the original commit "Always use 1366x768 viewport".
Signed-off-by: NChen Gang <chengang@emindsoft.com.cn>

dom/base/nsDocument.cpp

@@ -273,6 +273,8 @@ static LazyLogModule gCspPRLog("CSP");
 
 #define NAME_NOT_VALID ((nsSimpleContentList*)1)
 
+#define DISPLAY_WIDTH_HEITH_RATIO (946.0 / 1920.0)
+
 nsIdentifierMapEntry::~nsIdentifierMapEntry()
 {
 }
@@ -8198,6 +8200,11 @@ nsDocument::GetViewportInfo(const ScreenIntSize& aDisplaySize)
       size.height = std::max(size.height, displaySize.height);
     }
 
+    if (!aDisplaySize.IsEmpty()) {
+      size.width = aDisplaySize.width;
+      size.height = aDisplaySize.width * DISPLAY_WIDTH_HEITH_RATIO;
+    }
+
     return nsViewportInfo(scaleFloat, scaleMinFloat, scaleMaxFloat, size,
                           mAutoSize, effectiveAllowZoom);
   }

dom/base/nsViewportInfo.h

@@ -32,9 +32,7 @@ class MOZ_STACK_CLASS nsViewportInfo
       mAutoSize(true),
       mAllowZoom(aAllowZoom)
     {
-        //mSize = mozilla::ScreenSize(aDisplaySize) / mDefaultZoom;
-        mSize.width = 1366;
-        mSize.height = 768;
+        mSize = mozilla::ScreenSize(aDisplaySize) / mDefaultZoom;
         mozilla::CSSToLayoutDeviceScale pixelRatio(1.0f);
         mMinZoom = pixelRatio * kViewportMinScale;
         mMaxZoom = pixelRatio * kViewportMaxScale;
@@ -51,11 +49,10 @@ class MOZ_STACK_CLASS nsViewportInfo
                      mDefaultZoom(aDefaultZoom),
                      mMinZoom(aMinZoom),
                      mMaxZoom(aMaxZoom),
+                     mSize(aSize),
                      mAutoSize(aAutoSize),
                      mAllowZoom(aAllowZoom)
     {
-      mSize.width = 1366;
-      mSize.height = 768;
       ConstrainViewportValues();
     }