[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..4f2a9ee3c9b9f27a292e482c14f4a79d3b07752a 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"
@@ -606,6 +608,12 @@ struct CaseInsensitiveCompare {
   }
 };
 
+bool HasForcedTextDirectionSwitch() {

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

ditto nit: "// Get the cached switch presence; avoids repeated lookup in the
common case." (or you can inline this static bool in the function below)

[Kevin Bailey, 2017/05/01 21:21:42]

Done. Again, absorbed code.

+  static bool value = base::CommandLine::ForCurrentProcess()->HasSwitch(
+      switches::kForceTextDirection);
+  return value;
+}
+
 }  // namespace
 
 namespace internal {
@@ -1339,6 +1347,22 @@ SelectionModel RenderTextHarfBuzz::LastSelectionModelInsideRun(
   return SelectionModel(position, CURSOR_FORWARD);
 }
 
+void RenderTextHarfBuzz::CheckForcedDirection(UBiDiLevel* level) {

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

nit: "// Applies a forced direction if specified by a commandline switch."

[Kevin Bailey, 2017/05/01 21:21:42]

Done.

+  if (!HasForcedTextDirectionSwitch())
+    return;
+
+  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::kForceDirectionRTL)
+      *level = UBIDI_RTL;
+    if (force_flag == switches::kForceDirectionLTR)
+      *level = UBIDI_LTR;
+  }
+}
+
 void RenderTextHarfBuzz::ItemizeTextToRuns(
     const base::string16& text,
     internal::TextRunList* run_list_out) {
@@ -1382,6 +1406,7 @@ 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);
     // Odd BiDi embedding levels correspond to RTL runs.
     run->is_rtl = (run->level % 2) == 1;
     // Find the length and script of this script run.