Add hooks for GL_EXT_debug_marker in gpu

src/gpu/GrDrawTarget.cpp

Index: src/gpu/GrDrawTarget.cpp
diff --git a/src/gpu/GrDrawTarget.cpp b/src/gpu/GrDrawTarget.cpp
index 0909e08dc85cd0784c0a7fe0b7474d9c6588d086..2eb7bbb85ec93a9165a8356007f98cc1b8588ac3 100644
--- a/src/gpu/GrDrawTarget.cpp
+++ b/src/gpu/GrDrawTarget.cpp
@@ -971,6 +971,7 @@ void GrDrawTargetCaps::reset() {
     fPathRenderingSupport = false;
     fDstReadInShaderSupport = false;
     fReuseScratchTextures = true;
+    fDebugMarkerSupport = false;
 
     fMaxRenderTargetSize = 0;
     fMaxTextureSize = 0;
@@ -993,6 +994,7 @@ GrDrawTargetCaps& GrDrawTargetCaps::operator=(const GrDrawTargetCaps& other) {
     fPathRenderingSupport = other.fPathRenderingSupport;
     fDstReadInShaderSupport = other.fDstReadInShaderSupport;
     fReuseScratchTextures = other.fReuseScratchTextures;
+    fDebugMarkerSupport = other.fDebugMarkerSupport;
 
     fMaxRenderTargetSize = other.fMaxRenderTargetSize;
     fMaxTextureSize = other.fMaxTextureSize;
@@ -1019,6 +1021,7 @@ SkString GrDrawTargetCaps::dump() const {
     r.appendf("Path Rendering Support      : %s\n", gNY[fPathRenderingSupport]);
     r.appendf("Dst Read In Shader Support  : %s\n", gNY[fDstReadInShaderSupport]);
     r.appendf("Reuse Scratch Textures      : %s\n", gNY[fReuseScratchTextures]);
+    r.appendf("Debug Marker Support        : %s\n", gNY[fDebugMarkerSupport]);
     r.appendf("Max Texture Size            : %d\n", fMaxTextureSize);
     r.appendf("Max Render Target Size      : %d\n", fMaxRenderTargetSize);
     r.appendf("Max Sample Count            : %d\n", fMaxSampleCount);