Fixes moving fully occluded windows when the a11y keyboard shows.

TEST=WorkspaceLayoutManagerKeyboardTest.AdjustWindowForA11yKeyboard
BUG=407094

Review URL: https://codereview.chromium.org/506133002

Cr-Commit-Position: refs/heads/master@{#292056}

ash/wm/workspace/workspace_layout_manager.cc

@@ -153,12 +153,13 @@ void WorkspaceLayoutManager::OnKeyboardBoundsChanging(
     gfx::Rect window_bounds = ScreenUtil::ConvertRectToScreen(
         window_,
         window->GetTargetBounds());
-    gfx::Rect intersect = gfx::IntersectRects(window_bounds, new_bounds);
-    int shift = std::min(intersect.height(),
-                         window->bounds().y() - work_area_in_parent_.y());
+    int vertical_displacement =
+        std::max(0, window_bounds.bottom() - new_bounds.y());
+    int shift = std::min(vertical_displacement,
+                         window_bounds.y() - work_area_in_parent_.y());
     if (shift > 0) {
-      gfx::Point origin(window->bounds().x(), window->bounds().y() - shift);
-      SetChildBounds(window, gfx::Rect(origin, window->bounds().size()));
+      gfx::Point origin(window_bounds.x(), window_bounds.y() - shift);
+      SetChildBounds(window, gfx::Rect(origin, window_bounds.size()));
     }
   } else if (window_state->HasRestoreBounds()) {
     // Keyboard hidden, restore original bounds if they exist.

ash/wm/workspace/workspace_layout_manager_unittest.cc

@@ -1139,6 +1139,21 @@ TEST_F(WorkspaceLayoutManagerKeyboardTest, AdjustWindowForA11yKeyboard) {
   HideKeyboard();
   EXPECT_EQ(small_window_bound.ToString(), window->bounds().ToString());
 
+  gfx::Rect occluded_window_bounds(50,
+      keyboard_bounds.y() + keyboard_bounds.height()/2, 50,
+      keyboard_bounds.height()/2);
+  window->SetBounds(occluded_window_bounds);
+  EXPECT_EQ(occluded_window_bounds.ToString(),
+      occluded_window_bounds.ToString());
+  ShowKeyboard();
+  EXPECT_EQ(gfx::Rect(50,
+                      keyboard_bounds.y() - keyboard_bounds.height()/2,
+                      occluded_window_bounds.width(),
+                      occluded_window_bounds.height()).ToString(),
+            window->bounds().ToString());
+  HideKeyboard();
+  EXPECT_EQ(occluded_window_bounds.ToString(), window->bounds().ToString());
+
   Blur(&text_input_client);
 }