[rendertext,i18n] Added flag to force RTL rendering

ui/gfx/render_text_harfbuzz.cc

Index: ui/gfx/render_text_harfbuzz.cc
diff --git a/ui/gfx/render_text_harfbuzz.cc b/ui/gfx/render_text_harfbuzz.cc
index 042986f882721ba5c7876a7342d650335558d941..5de3cd6aa1257a54774754e5b5455f639c4efebc 100644
--- a/ui/gfx/render_text_harfbuzz.cc
+++ b/ui/gfx/render_text_harfbuzz.cc
@@ -7,6 +7,8 @@
 #include <limits>
 #include <set>
 
+#include "base/command_line.h"
+#include "base/i18n/base_i18n_switches.h"
 #include "base/i18n/bidi_line_iterator.h"
 #include "base/i18n/break_iterator.h"
 #include "base/i18n/char_iterator.h"
@@ -1339,6 +1341,19 @@ SelectionModel RenderTextHarfBuzz::LastSelectionModelInsideRun(
   return SelectionModel(position, CURSOR_FORWARD);
 }
 
+void RenderTextHarfBuzz::CheckForcedDirection(UBiDiLevel* level) {
+  base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
+  if (command_line->HasSwitch(switches::kForceTextDirection)) {
+    std::string force_flag =
+        command_line->GetSwitchValueASCII(switches::kForceTextDirection);
+
+    if (force_flag == switches::kForceUIDirectionRTL)
+      *level = UBIDI_RTL;
+    if (force_flag == switches::kForceUIDirectionLTR)
+      *level = UBIDI_LTR;
+  }
+}
+
 void RenderTextHarfBuzz::ItemizeTextToRuns(
     const base::string16& text,
     internal::TextRunList* run_list_out) {
@@ -1382,6 +1397,7 @@ void RenderTextHarfBuzz::ItemizeTextToRuns(
     int32_t script_item_break = 0;
     bidi_iterator.GetLogicalRun(run_break, &script_item_break, &run->level);
     CHECK_GT(static_cast<size_t>(script_item_break), run_break);
+    CheckForcedDirection(&run->level);

[msw, 2017/04/28 22:04:03]

I'm not sure this is needed; doesn't the underlying value come from
GetCharacterDirection? If this is needed; I'd (1) be curious as to why, and (2)
need you also cache the (presence of an) override value here too.

[Kevin Bailey, 2017/04/29 04:24:03]

'GetTextDirection()' is returning RTL, but, when the text contains 2 runs - a
bold one and a regular one - 'pBiDi->levels' is full of 2's, so 'run->level' is
always 2. I didn't dig deep enough into i18n to figure out why.

Done.

[msw, 2017/05/01 20:56:18]

Acknowledged.

     // Odd BiDi embedding levels correspond to RTL runs.
     run->is_rtl = (run->level % 2) == 1;
     // Find the length and script of this script run.