Fix overflow/underflow in gfx geometry once and for all

chrome/browser/chromeos/accessibility/accessibility_highlight_manager.cc

Index: chrome/browser/chromeos/accessibility/accessibility_highlight_manager.cc
diff --git a/chrome/browser/chromeos/accessibility/accessibility_highlight_manager.cc b/chrome/browser/chromeos/accessibility/accessibility_highlight_manager.cc
index 3af8b1f0338328ecdc3106f5435a5b83208b50fc..442ede7b59390cd0bd9d5bfa7cfafa10d6249cc2 100644
--- a/chrome/browser/chromeos/accessibility/accessibility_highlight_manager.cc
+++ b/chrome/browser/chromeos/accessibility/accessibility_highlight_manager.cc
@@ -15,13 +15,15 @@ namespace chromeos {
 
 namespace {
 
+// TODO: don't hide carets and focus ring "offscreen" by using large numbers.
 const gfx::Rect& OffscreenRect() {
-  CR_DEFINE_STATIC_LOCAL(const gfx::Rect, r, (INT_MIN, INT_MIN, 0, 0));
+  CR_DEFINE_STATIC_LOCAL(const gfx::Rect, r,
+                         (INT_MAX - 1000, INT_MAX - 1000, 0, 0));

[enne (OOO), 2016/09/23 00:17:06]

Surprisingly, AccessibilityHighlightManagerTest.TestFocusRingDrawsOrangePixels
depends on the fact that the offscreen rect is a large *positive* number when
inset by 40 pixels.  This is an integer underflow and undefined behavior.

If I make it INT_MIN + 1000, the test also fails but with a different error
(wrong pixels).  Therefore, it appears that this test relies on very specific
offscreen point values.  So, I've made it use large positive numbers with enough
of an offset that it won't overflow when inset by margins.

I'm kind of surprised that there's not some more straight forward way to convey
the information that the focus ring or caret should be invisible instead of just
placing it very far away.

[dmazzoni, 2016/10/04 22:29:32]

Working on a cleaner fix for this here:

https://codereview.chromium.org/2388093004/

   return r;
 }
 
 const gfx::Point& OffscreenPoint() {
-  CR_DEFINE_STATIC_LOCAL(const gfx::Point, p, (INT_MIN, INT_MIN));
+  CR_DEFINE_STATIC_LOCAL(const gfx::Point, p, (INT_MAX - 1000, INT_MAX - 1000));
   return p;
 }