gpu: workaround force_cube_map_positive_x_allocation fixes Android crash.

gpu/command_buffer/service/texture_manager.cc

Index: gpu/command_buffer/service/texture_manager.cc
diff --git a/gpu/command_buffer/service/texture_manager.cc b/gpu/command_buffer/service/texture_manager.cc
index ed0fd10e5b1e6e1ae96fc5b0316d0be8b10290fb..71aa3a05748ec4a8dda61875e2915d184c5995e1 100644
--- a/gpu/command_buffer/service/texture_manager.cc
+++ b/gpu/command_buffer/service/texture_manager.cc
@@ -1939,6 +1939,12 @@ void TextureManager::ValidateAndDoTexImage(
     return;
   }
 
+  if (texture_state->force_cube_map_positive_x_allocation) {
+    DoTexImage2DCubeMapPositiveXIfNeeded(texture_state, state->GetErrorState(),
+                                         framebuffer_state, function_name,
+                                         texture_ref, args);
+  }
+
   DoTexImage(texture_state, state->GetErrorState(), framebuffer_state,
              function_name, texture_ref, args);
 }
@@ -1955,6 +1961,40 @@ GLenum TextureManager::AdjustTexFormat(GLenum format) const {
   return format;
 }
 
+// Nexus 5 crashes on allocating a cube map texture bound to FBO, if
+// the CUBE_MAP_POSITIVE_X texture is not allocated yet.
+void TextureManager::DoTexImage2DCubeMapPositiveXIfNeeded(
+    DecoderTextureState* texture_state,
+    ErrorState* error_state,
+    DecoderFramebufferState* framebuffer_state,
+    const char* function_name,
+    TextureRef* texture_ref,
+    const DoTexImageArguments& args) {
+  switch (args.target) {
+    case GL_TEXTURE_CUBE_MAP_NEGATIVE_X:
+    case GL_TEXTURE_CUBE_MAP_POSITIVE_Y:
+    case GL_TEXTURE_CUBE_MAP_NEGATIVE_Y:
+    case GL_TEXTURE_CUBE_MAP_POSITIVE_Z:
+    case GL_TEXTURE_CUBE_MAP_NEGATIVE_Z:
+      break;
+    default:
+      return;
+  }
+
+  // ValidateTexImage is passed already.
+  Texture* texture = texture_ref->texture();
+  int width = 0;
+  int height = 0;
+  bool positive_x_level_defined = texture->GetLevelSize(
+      GL_TEXTURE_CUBE_MAP_POSITIVE_X, args.level, &width, &height, nullptr);
+  if (!positive_x_level_defined) {
+    DoTexImageArguments positive_x_args = args;

[no sievers, 2015/08/11 21:07:39]

I don't think we should use the pixels passed in with this API call to allocate
the pos_x face.
Can we maybe just use ClearLevel()? Then it would also take care of the clearing
logic and other potential redundant uploads.

[dshwang, 2015/08/12 08:06:09]

Good point. I'll reset pixels to nullptr like regular glTexImage(nullptr).
In nullptr case, TextureManager marks "unclear" to the texture, and then will
clear the texture later if needed.
We can not use ClearLevel(). ClearLevel() requires that the texture is defined.
we want to define the texture here. ClearLevel() attaches the texture to temp
FBO, and then calls glClear().

[no sievers, 2015/08/12 18:54:05]

I don't think it's true that it needs to be complete, see all the call sites to
ClearTextureLevel() from the decoder. Also it only does the glClear() if it's a
depth format as a workaround for Angle.

[dshwang, 2015/08/13 09:12:35]

Yes, I incorrectly explained the implementation detail. In general case,
glTexSubImage2D is used to clear the texture.
Anyway, the important point is that ClearLevel() doesn't call glTexImage2D.
ClearLevel() just clear the given texture. We need to define new texture here.

+    positive_x_args.target = GL_TEXTURE_CUBE_MAP_POSITIVE_X;
+    DoTexImage(texture_state, error_state, framebuffer_state, function_name,
+               texture_ref, positive_x_args);
+  }
+}
+
 void TextureManager::DoTexImage(
     DecoderTextureState* texture_state,
     ErrorState* error_state,