Allow multisampling without enabling GL_SAMPLE_COVERAGE.
Allow multisampling without enabling GL_SAMPLE_COVERAGE.

This setting is only used when an application wants to control which samples are written to.  If it is disabled, multisampling should just write to all samples.

BUG=38

Review URL: http://codereview.appspot.com/2194043

git-svn-id: a070b70d2b8c44c266a3870c0cddd9a0ee470458@431 736b8ea6-26fd-11df-bfd4-992fa37f6226

KTXSoftware/angleproject,ehsan/angle,shairai/angleproject,android-ia/platform_external_chromium_org_third_party_angle_dx11,vvuk/angle-old,crezefire/angle,shairai/angleproject,bsergean/angle,cantren/angleproject,android-ia/platform_external_chromium_org_third_party_angle,nandhanurrevanth/angle,pombreda/angleproject,MSOpenTech/angle-win8.0,geekboxzone/lollipop_external_chromium_org_third_party_angle,android-ia/platform_external_chromium_org_third_party_angle,shairai/angleproject,pombreda/angleproject,jgcaaprom/android_external_chromium_org_third_party_angle,geekboxzone/lollipop_external_chromium_org_third_party_angle,KTXSoftware/angleproject,RepublicMaster/angleproject,jgcaaprom/android_external_chromium_org_third_party_angle,KTXSoftware/angleproject,mrobinson/rust-angle,pombreda/angleproject,xuxiandi/angleproject,mlfarrell/angle,bsergean/angle,MIPS/external-chromium_org-third_party-angle_dx11,MSOpenTech/angle-win8.0,larsbergstrom/angle,domokit/waterfall,geekboxzone/lollipop_external_chromium_org_third_party_angle,mrobinson/rust-angle,MIPS/external-chromium_org-third_party-angle,stammen/angleproject,MIPS/external-chromium_org-third_party-angle_dx11,ecoal95/angle,RepublicMaster/angleproject,MSOpenTech/angle,csa7mdm/angle,jgcaaprom/android_external_chromium_org_third_party_angle,mrobinson/rust-angle,cantren/angleproject,themusicgod1/angleproject,android-ia/platform_external_chromium_org_third_party_angle_dx11,vvuk/angle-old,vvuk/angle-old,cvsuser-chromium/chromium-third-party_angle_dx11,mikolalysenko/angle,crezefire/angle,MIPS/external-chromium_org-third_party-angle,mybios/angle,MIPS/external-chromium_org-third_party-angle_dx11,themusicgod1/angleproject,vvuk/angle,themusicgod1/angleproject,mrobinson/rust-angle,nandhanurrevanth/angle,ghostoy/angle,ppy/angle,nandhanurrevanth/angle,ppy/angle,cantren/angleproject,csa7mdm/angle,ppy/angle,ghostoy/angle,stammen/angleproject,android-ia/platform_external_chromium_org_third_party_angle,csa7mdm/angle,xuxiandi/angleproject,ppy/angle,xin3liang/platform_external_chromium_org_third_party_angle,ecoal95/angle,xin3liang/platform_external_chromium_org_third_party_angle,crezefire/angle,KTXSoftware/angleproject,pombreda/angleproject,android-ia/platform_external_chromium_org_third_party_angle_dx11,domokit/waterfall,vvuk/angle,ehsan/angle,stammen/angleproject,mybios/angle,mlfarrell/angle,csa7mdm/angle,larsbergstrom/angle,xuxiandi/angleproject,mrobinson/rust-angle,xin3liang/platform_external_chromium_org_third_party_angle_dx11,KalebDark/angleproject,RepublicMaster/angleproject,cvsuser-chromium/chromium-third-party_angle_dx11,xin3liang/platform_external_chromium_org_third_party_angle_dx11,MIPS/external-chromium_org-third_party-angle,mlfarrell/angle,RepublicMaster/angleproject,xin3liang/platform_external_chromium_org_third_party_angle,cantren/angleproject,mybios/angle,vvuk/angle-old,ecoal95/angle,android-ia/platform_external_chromium_org_third_party_angle,xin3liang/platform_external_chromium_org_third_party_angle_dx11,crezefire/angle,ghostoy/angle,xuxiandi/angleproject,vvuk/angle,MSOpenTech/angle,larsbergstrom/angle,stammen/angleproject,MSOpenTech/angle,ecoal95/angle,ehsan/angle,KalebDark/angleproject,themusicgod1/angleproject,shairai/angleproject,xin3liang/platform_external_chromium_org_third_party_angle,larsbergstrom/angle,bsergean/angle,xin3liang/platform_external_chromium_org_third_party_angle_dx11,KalebDark/angleproject,android-ia/platform_external_chromium_org_third_party_angle_dx11,geekboxzone/lollipop_external_chromium_org_third_party_angle,ehsan/angle,ecoal95/angle,cvsuser-chromium/chromium-third-party_angle_dx11,mikolalysenko/angle,mybios/angle,ghostoy/angle,KTXSoftware/angleproject,mikolalysenko/angle,bsergean/angle,jgcaaprom/android_external_chromium_org_third_party_angle,mlfarrell/angle,MIPS/external-chromium_org-third_party-angle,cvsuser-chromium/chromium-third-party_angle_dx11,vvuk/angle,MSOpenTech/angle-win8.0,MIPS/external-chromium_org-third_party-angle_dx11,MSOpenTech/angle,KalebDark/angleproject,MSOpenTech/angle-win8.0,mikolalysenko/angle,nandhanurrevanth/angle