uikit_uitls and ui_uitls addditions.

This CL adds some utility functions that enable operating on common
UIKit and CoreGraphics data structures using the language-direction-
independent 'leading' and 'trailing' nomenclature.

These utilities will be used for iOS9 RTL support downstream.

BUG=520568

Review URL: https://codereview.chromium.org/1303013008

Cr-Commit-Position: refs/heads/master@{#345595}

ios/chrome/browser/ui/rtl_geometry.h

@@ -94,7 +94,19 @@ LayoutRect LayoutRectGetTrailingLayout(LayoutRect layout);
 // Return the trailing extent of |layout| (its leading plus its width).
 CGFloat LayoutRectGetTrailingEdge(LayoutRect layout);
 
-// Utilities for mapping UIKit geometric structures to RTL-independent
+// Utilities for mapping UIKit geometric structures to RTL-independent geometry.
+
+// Get leading and trailing edges of |rect|, assuming layout direction
+// |direction|.
+CGFloat CGRectGetLeadingEdgeUsingDirection(CGRect rect,
+                                           base::i18n::TextDirection direction);
+CGFloat CGRectGetTrailingEdgeUsingDirection(
+    CGRect rect,
+    base::i18n::TextDirection direction);
+
+// As above, with |direction| == LayoutDirection().
+CGFloat CGRectGetLeadingEdge(CGRect rect);
+CGFloat CGRectGetTrailingEdge(CGRect rect);
 
 // Leading/trailing autoresizing masks. 'Leading' is 'Left' under iOS <= 8 or
 // in an LTR language, 'Right' otherwise; 'Trailing' is the obverse.
@@ -116,6 +128,11 @@ UIEdgeInsets UIEdgeInsetsMakeDirected(CGFloat top,
                                       CGFloat bottom,
                                       CGFloat trailing);
 
+// Inverses of the above functions: return the leading/trailing inset for
+// the current direction.
+CGFloat UIEdgeInsetsGetLeading(UIEdgeInsets insets);
+CGFloat UIEdgeInsetsGetTrailing(UIEdgeInsets insets);
+
 // Autolayout utilities
 
 // Returns the correct NSLayoutFormatOption for the current OS and build. This

ios/chrome/browser/ui/rtl_geometry.mm

@@ -116,6 +116,28 @@ CGFloat LayoutRectGetTrailingEdge(LayoutRect layout) {
 
 #pragma mark - UIKit utilities
 
+CGFloat CGRectGetLeadingEdgeUsingDirection(
+    CGRect rect,
+    base::i18n::TextDirection direction) {
+  return direction == base::i18n::RIGHT_TO_LEFT ? CGRectGetMaxX(rect)
+                                                : CGRectGetMinX(rect);
+}
+
+CGFloat CGRectGetTrailingEdgeUsingDirection(
+    CGRect rect,
+    base::i18n::TextDirection direction) {
+  return direction == base::i18n::RIGHT_TO_LEFT ? CGRectGetMinX(rect)
+                                                : CGRectGetMaxX(rect);
+}
+
+CGFloat CGRectGetLeadingEdge(CGRect rect) {
+  return CGRectGetLeadingEdgeUsingDirection(rect, LayoutDirection());
+}
+
+CGFloat CGRectGetTrailingEdge(CGRect rect) {
+  return CGRectGetTrailingEdgeUsingDirection(rect, LayoutDirection());
+}
+
 UIViewAutoresizing UIViewAutoresizingFlexibleLeadingMargin() {
   return base::i18n::IsRTL() && base::ios::IsRunningOnIOS9OrLater()
              ? UIViewAutoresizingFlexibleRightMargin
@@ -150,6 +172,14 @@ UIEdgeInsets UIEdgeInsetsMakeDirected(CGFloat top,
                                         LayoutDirection());
 }
 
+CGFloat UIEdgeInsetsGetLeading(UIEdgeInsets insets) {
+  return UseRTLLayout() ? insets.right : insets.left;
+}
+
+CGFloat UIEdgeInsetsGetTrailing(UIEdgeInsets insets) {
+  return UseRTLLayout() ? insets.left : insets.right;
+}
+
 #pragma mark - autolayout utilities
 
 NSLayoutFormatOptions LayoutOptionForRTLSupport() {