Implement all resolution change policies for desktop and tab capture.

media/base/video_util.cc

Index: media/base/video_util.cc
diff --git a/media/base/video_util.cc b/media/base/video_util.cc
index d7946743eae091cef3f9952c4a0d6cb5acd4ab40..e04a5a3c5439538f2f9f7d91578b8fea63aa86bd 100644
--- a/media/base/video_util.cc
+++ b/media/base/video_util.cc
@@ -270,6 +270,23 @@ void RotatePlaneByPixels(
   }
 }
 
+// Common logic for the letterboxing and scale-within/scale-encompassing
+// functions.  Scales |size| to either fit within or encompass |target|,
+// depending on whether |fit_within_target| is true.
+static gfx::Size ScaleSizeToTarget(const gfx::Size& size,
+                                   const gfx::Size& target,
+                                   bool fit_within_target) {
+  if (size.IsEmpty())
+    return gfx::Size();  // Corner case: Aspect ratio is undefined.
+
+  const int64 x = static_cast<int64>(size.width()) * target.height();
+  const int64 y = static_cast<int64>(size.height()) * target.width();
+  const bool use_target_width = fit_within_target ? (y < x) : (x < y);
+  return use_target_width ?
+      gfx::Size(target.width(), static_cast<int>(y / size.width())) :
+      gfx::Size(static_cast<int>(x / size.height()), target.height());
+}
+
 gfx::Rect ComputeLetterboxRegion(const gfx::Rect& bounds,
                                  const gfx::Size& content) {
   // If |content| has an undefined aspect ratio, let's not try to divide by
@@ -277,19 +294,33 @@ gfx::Rect ComputeLetterboxRegion(const gfx::Rect& bounds,
   if (content.IsEmpty())
     return gfx::Rect();
 
-  int64 x = static_cast<int64>(content.width()) * bounds.height();
-  int64 y = static_cast<int64>(content.height()) * bounds.width();
-
-  gfx::Size letterbox(bounds.width(), bounds.height());
-  if (y < x)
-    letterbox.set_height(static_cast<int>(y / content.width()));
-  else
-    letterbox.set_width(static_cast<int>(x / content.height()));
   gfx::Rect result = bounds;
-  result.ClampToCenteredSize(letterbox);
+  result.ClampToCenteredSize(ScaleSizeToTarget(content, bounds.size(), true));
   return result;
 }
 
+gfx::Size ScaleSizeToFitWithinTarget(const gfx::Size& size,
+                                     const gfx::Size& target) {
+  return ScaleSizeToTarget(size, target, true);
+}
+
+gfx::Size ScaleSizeToEncompassTarget(const gfx::Size& size,
+                                     const gfx::Size& target) {
+  return ScaleSizeToTarget(size, target, false);
+}
+
+gfx::Size PadToMatchAspectRatio(const gfx::Size& size,
+                                const gfx::Size& target) {
+  if (target.IsEmpty())
+    return gfx::Size();  // Aspect ratio is undefined.
+
+  const int64 x = static_cast<int64>(size.width()) * target.height();
+  const int64 y = static_cast<int64>(size.height()) * target.width();
+  if (x < y)
+    return gfx::Size(static_cast<int>(y / target.height()), size.height());
+  return gfx::Size(size.width(), static_cast<int>(x / target.width()));
+}
+
 void CopyRGBToVideoFrame(const uint8* source,
                          int stride,
                          const gfx::Rect& region_in_frame,