Fix the alignment issue with Arabic when a font has kerning or cursive gsub

Patch by behdad@chromium.org.



Will add a webkit layout test for Arabic alignment as soon as we find
a font that can be included in Webkit LayoutTests.

BUG=105685
TEST= http://www.bbcarabic.com should be rendered the same way as is done by Firefox on Linux. Paragraphs should be right justified and should not overlap with photos or other elements next to them.  See the screenshots attached in the bug report.
TBR=bashik

Review URL: https://chromiumcodereview.appspot.com/10382212

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@138001 0039d316-1c4b-4281-b951-d872f2087c98

third_party/harfbuzz/README.chromium

@@ -18,3 +18,5 @@ changes against upstream; you must also apply any changes that you make to
 the checked-in copy of the source.)
 
 Added support for building on Android.
+
+The patch for Arabic alignment bug was added (bug 105685).

third_party/harfbuzz/chromium.patch

@@ -133,3 +133,26 @@ index 847ac52..6f9a55b 100644
  
  static const HB_OpenTypeFeature tibetan_features[] = {
      { HB_MAKE_TAG('c', 'c', 'm', 'p'), CcmpProperty },
+diff --git a/src/harfbuzz-shaper.cpp b/src/harfbuzz-shaper.cpp
+index ce4d4ac..6b4d6d2 100644
+--- a/src/harfbuzz-shaper.cpp
++++ b/src/harfbuzz-shaper.cpp
+@@ -1263,16 +1263,13 @@ HB_Bool HB_OpenTypePosition(HB_ShaperItem *item, int availableGlyphs, HB_Bool do
+ //                    (int)(positions[i].x_pos >> 6), (int)(positions[i].y_pos >> 6),
+ //                    positions[i].back, positions[i].new_advance);
+ 
+-            HB_Fixed adjustment = (item->item.bidiLevel % 2) ? -positions[i].x_advance : positions[i].x_advance;
++            HB_Fixed adjustment = positions[i].x_advance;
+ 
+             if (!(face->current_flags & HB_ShaperFlag_UseDesignMetrics))
+                 adjustment = HB_FIXED_ROUND(adjustment);
+ 
+-            if (positions[i].new_advance) {
+-                advances[i] = adjustment;
+-            } else {
++            if (positions[i].new_advance == 0)
+                 advances[i] += adjustment;
+-            }
+ 
+             int back = 0;
+             HB_FixedPoint *offsets = item->offsets;

third_party/harfbuzz/src/harfbuzz-shaper.cpp

@@ -1282,16 +1282,13 @@ HB_Bool HB_OpenTypePosition(HB_ShaperItem *item, int availableGlyphs, HB_Bool do
 //                    (int)(positions[i].x_pos >> 6), (int)(positions[i].y_pos >> 6),
 //                    positions[i].back, positions[i].new_advance);
 
-            HB_Fixed adjustment = (item->item.bidiLevel % 2) ? -positions[i].x_advance : positions[i].x_advance;
+            HB_Fixed adjustment = positions[i].x_advance;
 
             if (!(face->current_flags & HB_ShaperFlag_UseDesignMetrics))
                 adjustment = HB_FIXED_ROUND(adjustment);
 
-            if (positions[i].new_advance) {
-                advances[i] = adjustment;
-            } else {
+            if (positions[i].new_advance == 0)
                 advances[i] += adjustment;
-            }
 
             int back = 0;
             HB_FixedPoint *offsets = item->offsets;
@@ -1354,4 +1351,3 @@ HB_Bool HB_ShapeItem(HB_ShaperItem *shaper_item)
     shaper_item->glyphIndicesPresent = false;
     return result;
 }
-