Fix GLHelperReadbackSupport::SupportsFormat crash

content/common/gpu/client/gl_helper_readback_support.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/common/gpu/client/gl_helper_readback_support.h"
 #include "base/logging.h"
 #include "gpu/GLES2/gl2extchromium.h"
 #include "third_party/skia/include/core/SkImageInfo.h"
 
 namespace content {
@@ skipping 77 matching lines @@
                                                              dst_framebuffer);
   gl_->FramebufferTexture2D(
       GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, dst_texture, 0);
   GLint format_tmp = 0, type_tmp = 0;
   gl_->GetIntegerv(GL_IMPLEMENTATION_COLOR_READ_FORMAT, &format_tmp);
   gl_->GetIntegerv(GL_IMPLEMENTATION_COLOR_READ_TYPE, &type_tmp);
   *format_out = format_tmp;
   *type_out = type_tmp;
 
   struct FormatCacheEntry entry = { format, type, *format_out, *type_out };
   format_cache_.push_back(entry);

[no sievers, 2014/10/08 21:27:13]

Should we also not do this if format_out and type_out are 0?

 }
 
 bool GLHelperReadbackSupport::SupportsFormat(GLenum format, GLenum type) {
   // GLES2.0 Specification says this pairing is always supported
   // with additional format from GL_IMPLEMENTATION_COLOR_READ_FORMAT/TYPE
   if (format == GL_RGBA && type == GL_UNSIGNED_BYTE)
     return true;
 
   if (format == GL_BGRA_EXT && type == GL_UNSIGNED_BYTE) {
     const GLubyte* tmp = gl_->GetString(GL_EXTENSIONS);
-    std::string extensions =
-        " " + std::string(reinterpret_cast<const char*>(tmp)) + " ";
-    if (extensions.find(" GL_EXT_read_format_bgra ") != std::string::npos) {
-      return true;
+    if (tmp) {
+      std::string extensions =
+          " " + std::string(reinterpret_cast<const char*>(tmp)) + " ";
+      if (extensions.find(" GL_EXT_read_format_bgra ") != std::string::npos) {
+        return true;
+      }
     }
   }
 
   bool supports_format = false;
   GLenum ext_format = 0, ext_type = 0;
   GetAdditionalFormat(format, type, &ext_format, &ext_type);
   if ((ext_format == format) && (ext_type == type)) {
     supports_format = true;
   }
   return supports_format;
@@ skipping 49 matching lines @@
       return GLHelperReadbackSupport::NOT_SUPPORTED;
     default:
       NOTREACHED();
       break;
   }
 
   return GLHelperReadbackSupport::NOT_SUPPORTED;
 }
 
 }  // namespace content