Possible deferencing from nullptrs in AtkComponent interface.

Make sure AtkComponent interface callbacks operate on valid pointers.
GetExtent and GetPosition are almost the same. Reducing some code
by adding helper method SetExtentsRelativeToAtkCoordinateType.

BUG=463671

Review URL: https://codereview.chromium.org/1129813004

Cr-Commit-Position: refs/heads/master@{#329664}

ui/accessibility/platform/ax_platform_node_auralinux.cc

@@ -204,7 +204,17 @@ static void ax_platform_node_auralinux_get_extents(AtkComponent* atk_component,
                                                    gint* x, gint* y,
                                                    gint* width, gint* height,
                                                    AtkCoordType coord_type) {
-  *x = *y = *width = *height = 0;
+  g_return_if_fail(ATK_IS_COMPONENT(atk_component));
+
+  if (x)
+    *x = 0;
+  if (y)
+    *y = 0;
+  if (width)
+    *width = 0;
+  if (height)
+    *height = 0;
+
   AtkObject* atk_object = ATK_OBJECT(atk_component);
   ui::AXPlatformNodeAuraLinux* obj =
       AtkObjectToAXPlatformNodeAuraLinux(atk_object);
@@ -217,7 +227,13 @@ static void ax_platform_node_auralinux_get_extents(AtkComponent* atk_component,
 static void ax_platform_node_auralinux_get_position(AtkComponent* atk_component,
                                                     gint* x, gint* y,
                                                     AtkCoordType coord_type) {
-  *x = *y = 0;
+  g_return_if_fail(ATK_IS_COMPONENT(atk_component));
+
+  if (x)
+    *x = 0;
+  if (y)
+    *y = 0;
+
   AtkObject* atk_object = ATK_OBJECT(atk_component);
   ui::AXPlatformNodeAuraLinux* obj =
       AtkObjectToAXPlatformNodeAuraLinux(atk_object);
@@ -229,7 +245,13 @@ static void ax_platform_node_auralinux_get_position(AtkComponent* atk_component,
 
 static void ax_platform_node_auralinux_get_size(AtkComponent* atk_component,
                                                 gint* width, gint* height) {
-  *width = *height = 0;
+  g_return_if_fail(ATK_IS_COMPONENT(atk_component));
+
+  if (width)
+    *width = 0;
+  if (height)
+    *height = 0;
+
   AtkObject* atk_object = ATK_OBJECT(atk_component);
   ui::AXPlatformNodeAuraLinux* obj =
       AtkObjectToAXPlatformNodeAuraLinux(atk_object);
@@ -465,43 +487,50 @@ int AXPlatformNodeAuraLinux::GetIndexInParent() {
   return 0;
 }
 
-void AXPlatformNodeAuraLinux::GetExtents(gint* x, gint* y,
-                                         gint* width, gint* height,
-                                         AtkCoordType coord_type) {
+void AXPlatformNodeAuraLinux::SetExtentsRelativeToAtkCoordinateType(
+    gint* x, gint* y, gint* width, gint* height, AtkCoordType coord_type) {
   gfx::Rect extents = GetBoundsInScreen();
 
-  *x = extents.x();
-  *y = extents.y();
-  *width = extents.width();
-  *height = extents.height();
+  if (x)
+    *x = extents.x();
+  if (y)
+    *y = extents.y();
+  if (width)
+    *width = extents.width();
+  if (height)
+    *height = extents.height();
 
   if (coord_type == ATK_XY_WINDOW) {
     AtkObject* atk_object = GetParent();
     gfx::Point window_coords = FindAtkObjectParentCoords(atk_object);
-    *x -= window_coords.x();
-    *y -= window_coords.y();
+    if (x)
+      *x -= window_coords.x();
+    if (y)
+      *y -= window_coords.y();
   }
 }
 
+void AXPlatformNodeAuraLinux::GetExtents(gint* x, gint* y,
+                                         gint* width, gint* height,
+                                         AtkCoordType coord_type) {
+  SetExtentsRelativeToAtkCoordinateType(x, y,
+                                        width, height,
+                                        coord_type);
+}
+
 void AXPlatformNodeAuraLinux::GetPosition(gint* x, gint* y,
                                           AtkCoordType coord_type) {
-  gfx::Rect rect_pos = GetBoundsInScreen();
-
-  *x = rect_pos.x();
-  *y = rect_pos.y();
-
-  if (coord_type == ATK_XY_WINDOW) {
-    AtkObject* atk_object = GetParent();
-    gfx::Point window_coords = FindAtkObjectParentCoords(atk_object);
-    *x -= window_coords.x();
-    *y -= window_coords.y();
-  }
+  SetExtentsRelativeToAtkCoordinateType(x, y,
+                                        nullptr,nullptr,
+                                        coord_type);
 }
 
 void AXPlatformNodeAuraLinux::GetSize(gint* width, gint* height) {
   gfx::Rect rect_size = GetData().location;
-  *width = rect_size.width();
-  *height = rect_size.height();
+  if (width)
+    *width = rect_size.width();
+  if (height)
+    *height = rect_size.height();
 }
 
 }  // namespace ui

ui/accessibility/platform/ax_platform_node_auralinux.h

@@ -39,6 +39,10 @@ class AXPlatformNodeAuraLinux : public AXPlatformNodeBase {
   void GetPosition(gint* x, gint* y, AtkCoordType coord_type);
   void GetSize(gint* width, gint* height);
 
+  void SetExtentsRelativeToAtkCoordinateType(
+      gint* x, gint* y, gint* width, gint* height,
+      AtkCoordType coord_type);
+
   // AXPlatformNode overrides.
   void Destroy() override;
   gfx::NativeViewAccessible GetNativeViewAccessible() override;