Adding proper dragging behavior for L/R maximized windows.

ash/wm/frame_painter.cc

Index: ash/wm/frame_painter.cc
diff --git a/ash/wm/frame_painter.cc b/ash/wm/frame_painter.cc
index 244ba858264e339c06aa79846999adec5ad6e943..6fae61d2875285d5e5fdc19b01c8a02624a67bc4 100644
--- a/ash/wm/frame_painter.cc
+++ b/ash/wm/frame_painter.cc
@@ -7,6 +7,7 @@
 #include "ash/ash_constants.h"
 #include "ash/shell.h"
 #include "ash/shell_window_ids.h"
+#include "ash/wm/property_util.h"
 #include "ash/wm/window_util.h"
 #include "ash/wm/workspace_controller.h"
 #include "base/logging.h"  // DCHECK
@@ -26,6 +27,7 @@
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/font.h"
 #include "ui/gfx/image/image.h"
+#include "ui/gfx/screen.h"
 #include "ui/views/controls/button/image_button.h"
 #include "ui/views/widget/widget.h"
 #include "ui/views/widget/widget_delegate.h"
@@ -246,6 +248,7 @@ int FramePainter::NonClientHitTest(views::NonClientFrameView* view,
                                                      kResizeAreaCornerSize,
                                                      kResizeAreaCornerSize,
                                                      can_ever_resize);
+  frame_component = AdjustFrameHitCodeForMaximizedModes(frame_component);
   if (frame_component != HTNOWHERE)
     return frame_component;
 
@@ -594,6 +597,43 @@ int FramePainter::GetHeaderOpacity(HeaderMode header_mode,
   return kInactiveWindowOpacity;
 }
 
+int FramePainter::AdjustFrameHitCodeForMaximizedModes(int hit_code) {
+  if (hit_code != HTNOWHERE && wm::IsWindowNormal(window_) &&
+      GetRestoreBoundsInScreen(window_)) {
+    // When there is a restore rectangle, a left/right maximized window might
+    // be active.
+    const gfx::Rect& bounds = frame_->GetWindowBoundsInScreen();
+    const gfx::Rect& screen =
+        gfx::Screen::GetDisplayMatching(bounds).work_area();
+    if (bounds.y() == screen.y() && bounds.bottom() == screen.bottom()) {
+      // The window is probably either left or right maximized.
+      if (bounds.x() == screen.x()) {
+        // It is left maximized and we can only allow a right resize.
+        return (hit_code == HTBOTTOMRIGHT ||
+                hit_code == HTTOPRIGHT ||
+                hit_code == HTRIGHT) ? HTRIGHT : HTNOWHERE;
+      } else if (bounds.right() == screen.right()) {
+        // It is right maximized and we can only allow a left resize.
+        return (hit_code == HTBOTTOMLEFT ||
+                hit_code == HTTOPLEFT ||
+                hit_code == HTLEFT) ? HTLEFT : HTNOWHERE;
+      }
+    } else if (bounds.x() == screen.x() &&
+               bounds.right() == screen.right()) {
+      // If horizontal fill mode is activated we don't allow a left/right
+      // resizing.
+      if (hit_code == HTTOPRIGHT ||
+          hit_code == HTTOP ||
+          hit_code == HTTOPLEFT)
+        return HTTOP;
+      return (hit_code == HTBOTTOMRIGHT ||
+              hit_code == HTBOTTOM ||
+              hit_code == HTBOTTOMLEFT) ? HTBOTTOM : HTNOWHERE;
+    }
+  }
+  return hit_code;
+}
+
 // static
 bool FramePainter::UseSoloWindowHeader() {
   if (!instances_)