fix --show-composited-layer-borders on Mac

gpu/command_buffer/service/gles2_cmd_decoder.cc

Index: gpu/command_buffer/service/gles2_cmd_decoder.cc
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.cc b/gpu/command_buffer/service/gles2_cmd_decoder.cc
index a5946fab874cafdcba455ea0d5bcfa4bb081ef31..e212df442fa72fa8e11a69b8cf15b96e7f65f387 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -1666,7 +1666,7 @@ class GLES2DecoderImpl : public GLES2Decoder, public ErrorStateClient {
   bool DoIsPathCHROMIUM(GLuint client_id);
   bool DoIsSync(GLuint client_id);
 
-  void DoLineWidth(GLfloat width);
+  GLfloat DoLineWidth(GLfloat width);
 
   // Wrapper for glLinkProgram
   void DoLinkProgram(GLuint program);
@@ -8455,9 +8455,27 @@ void GLES2DecoderImpl::DoRenderbufferStorage(
   }
 }
 
-void GLES2DecoderImpl::DoLineWidth(GLfloat width) {
-  glLineWidth(
-      std::min(std::max(width, line_width_range_[0]), line_width_range_[1]));
+error::Error GLES2DecoderImpl::HandleLineWidth(uint32_t immediate_data_size,
+                                               const volatile void* cmd_data) {
+  const volatile gles2::cmds::LineWidth& c =
+      *static_cast<const volatile gles2::cmds::LineWidth*>(cmd_data);
+  GLfloat width = static_cast<GLfloat>(c.width);
+  if (width <= 0.0f || std::isnan(width)) {
+    LOCAL_SET_GL_ERROR(GL_INVALID_VALUE, "LineWidth", "width out of range");
+    return error::kNoError;
+  }
+  if (state_.line_width != width) {
+    // Save adjusted line width.
+    state_.line_width = DoLineWidth(width);

[piman, 2016/11/07 19:38:01]

This is incorrect, though, because it means the value returned by
glGetIIntegerv(GL_LINE_WIDTH, ...) will not match the value passed to
glLineWidth any more (it's supposed to).

We either need to keep both the original value and the clamped value, or we need
to do the clamping again in ContextState::InitState

+  }
+  return error::kNoError;
+}
+
+GLfloat GLES2DecoderImpl::DoLineWidth(GLfloat width) {
+  GLfloat real_width =
+      std::min(std::max(width, line_width_range_[0]), line_width_range_[1]);
+  glLineWidth(real_width);
+  return real_width;
 }
 
 void GLES2DecoderImpl::DoLinkProgram(GLuint program_id) {